Ridha Bouallegue

Hybrid TOA/AOA approximate maximum likelihood mobile localization

This letter deals with a hybrid time-of-arrival/angle-of-arrival (TOA/AOA) approximate maximum likelihood (AML) wireless location algorithm. Thanks to the use of both TOA/AOA measurements, the proposed technique can rely on two base stations (BS) only and achieves better performance compared to the original approximate maximum likelihood (AML) method. The use of two BSs is an important advantage in wireless cellular communication systems because it avoids hearability problems and reduces network signaling burden. Simulation results show that, for certain scenarios, the proposed hybrid TOA/AOA AML with two BSs can outperform the AML with up to six BSs.

Hybrid TOA/AOA mobile localization with NLOS mitigation in ring scattering environments

This paper deals with locating mobile stations (MS) under non-line-of-sight (NLOS) propagation environments. Based on the ring of scatterers (ROS) Leepsilas model, the proposed positioning technique can effectively mitigate the NLOS error bias by using time of arrival/angle of arrival (TOA/AOA) measurements of only two base stations (BS). Simulation results show that the proposed technique outperforms conventional least squares algorithms by offering an accuracy enhancement of about 25%.

A fast color image encryption scheme based on multidimensional chaotic maps

In this paper, we propose a new color image encryption technique using two multidimensional chaotic maps: a three dimensional chaotic map for the key expansion and a two dimensional chaotic map for the generation of two chaotic lookup tables. The experimental results demonstrate that the distributions of red, green and blue surfaces of the encrypted image have a random-like behavior. Simulations show also that the proposed encryption scheme is particularly suitable for high speed applications.

Mobile Localization Under Non-Line-of-Sight Conditions Using Scattering Information

A novel mobile localization algorithm under non-line-of-sight (NLoS) conditions involving at most two base stations (BS) is presented. By using such a small number of BSs, the proposed technique avoids problems related to weak mobile hearability and excessive network messaging overload. Based on a scattering model, the NLoS hybrid approximate maximum likelihood (NLoS HAML) approach presented herein estimates the distances between the mobile station (MS) and the scatterers through the measured hybrid time-of-arrival/angle-of-arrival (ToA/AoA) statistics. Then, it matches the calculated distances to a known scatterers’ distribution in a maximum likelihood (ML) sense. Numerical results prove that the proposed algorithm outperforms previous methods by providing an accuracy enhancement that reaches 60%. It is also shown that the performance enhancement provided by the proposed algorithm is maximized when the adequate scatterers distribution is adopted.

A novel scattering distance-based mobile positioning algorithm

We present in this paper a new mobile location algorithm. Mobile location in cellular networks using time-ofarrival/ angle-of-arrival (ToA/AoA) data from a single base station (BS) only (namely the home serving BS) is a promising new approach, not yet thoroughly studied in the literature. In this context, the scattering distance-based (SDB) algorithm proposed herein, locates the MS by identifying the calculated distance between scatterers in the case of ring-of-scatterers (RoS) model. The obtained relationship between the MS and the scatterers positions provides an additional information that enhances the estimate accuracy. Simulation results show that the proposed SDB algorithm outperforms the other methods applicable in the same context.

OFDM synchronization errors and effects of phase noise on WLAN transceivers

This work aims at frequency synchronization in OFDM IEEE 802.11g Transceivers. The degradation of performance results from the detrimental effects introduced by frequency offset and phase noise. First, we present a robust method to detect and synchronize the OFDM signal with severe noise and interference corruption based on calculating the accumulated phase difference for each subcarrier. Then, we present a simple architecture to implement the proposed methods. These methods are simulated and analyzed by computer. Finally, we propose many algorithms to correct the common phase error (CPE) of the phase noise and track well its variation.