Abdelmadjid Maali

Adaptive CA-CFAR threshold for non-coherent IR-UWB energy detector receivers

In the present letter, a new adaptive threshold comparison approach for time-of-arrival (TOA) estimation in ultra wideband (UWB) signals is proposed. This approach can be used with non-coherent energy detector receivers in UWB systems. It exploits the idea of cell averaging constant false alarm rate (CA-CFAR) used in radar systems, where the threshold changes every energy block. The performance of several approaches are compared via Monte Carlo simulations using the CM1 channel model of the standard IEEE 802.15.4a. Both simulation results and comparisons are provided highlighting the effectiveness of the proposed approach.

A new low complexity NLOS identification approach based on UWB energy detection

The major problem of indoor localization is the presence of Non-line-of-sight (NLOS) channels. In order to perform the NLOS identification, this paper proposes a new NLOS identification approach. It is based on the energy statistics of the direct-path pulse (DPP) and on the statistics of the delay between the strongest-energy pulse and the DPP energy of the received signal folded version. The simplicity of the proposed approach lies in the use of the parameters of the Energy-Based time of arrival (TOA) Estimation (EBE) algorithm. The CM1 and CM2 channel models of the standard IEEE802.15.4a are used. Numerical simulations results show that the correct identification of channel models with the proposed approach is better than with the multipath channel statistics based approach.

Joint TOA Estimation and NLOS Identification for UWB Localization Systems

In this paper, we propose a new joint time-of-arrival estimation and non-line-of-sight identification approach for ultra-wideband wireless sensor network applications. We use an energy-based time-of-arrival estimation algorithm. The non-line-of-sight detection is based on the direct path to the strongest multipath components ratio of the received signal folded version of the energy-based time-of-arrival estimation algorithm. The non-line-of-sight information is used in the weighted least-squares localization algorithm. The channel models residential LOS and residential NLOS of the standard IEEE802.15.4a are used. Numerical simulations results show that the correct identification of channel models with the proposed approach is better than those based on joint likelihood ratio and the location accuracy obtained by weighted least-squares algorithm using non-line-of-sight information is higher than that obtained by least-square algorithm.

An evaluation of UWB localization under non line-of-sight (NLOS) propagation

In this paper we evaluate the statistical performances of the association of a low-complexity of the time of arrival (TOA) estimation algorithm and the location estimation algorithm in a non line-of-sight (NLOS) indoor environment. For that, we choose the time hopping (TH) code and pulse amplitude modulation (PAM) for ultra wideband (UWB) symbols and the IEEE802.15.3a models (CM1 and CM3) for the channel propagation. The numerical simulations show that the accuracy of TOA estimation can be achieved with only one training symbol period for data aided (DA) mode in LOS propagation (CM1). These performances are seriously degraded in NLOS propagation (CM3). Otherwise, the obtained results show the harmful effect of increasing the number of NLOS nodes (basic stations) on the positioning accuracy.

CA-CFAR threshold selection for IR-UWB TOA estimation

In this paper, we simplify the architecture of the cell averaging constant false alarm rate (CA-CFAR) approach used in time-of-arrival (TOA) estimation for impulse radio ultra wideband (IR-UWB) systems. The CA-CFAR approach uses the received signal samples provided by the non-coherent energy detection (ED) receivers. The modified approach is evaluated by Monte Carlo simulation on the CM1 channel model of the standard IEEE802.15.4a. The effects of the reference cells number and the guard cells duration on the performances of the modified CA-CFAR approach are studied. The simulation demonstrates that the modified approach gives better results than the conventional approaches.

Improved energy detection receiver for ranging in IEEE 802.15.4a standard

In this paper, we propose a novel energy detection (ED) receiver architecture combined with time-of-arrival (TOA) estimation algorithm, compliant to the IEEE 802.15.4a standard. The architecture is based on double overlapping integrators and a sliding correlator. It exploits a series of ternary preamble sequences with perfect autocorrelation property. This property ensures coding gain, which allows an accurate estimation of power delay profile (PDP). To improve TOA estimation, the interpolation of PDP samples is proposed and the architecture is validated by using an ultra-wideband signals measurements platform. These measurements are carried out in line-of-sight and non-line-of-sight multipath environments. The experimental results show that the ranging performances obtained by the proposed architecture are higher than those obtained by the conventional architecture based on a single-integrator in both LOS and NLOS environments.

Impulsive acoustic source localization via wireless sensor Imote2

In this paper, we are interested in localizing acoustic sources such as gunfire of Automatic Pistol (AP) and Kalashnikov AK-47 via the Imote2 wireless sensor node platform, using an array of four synchronized microphones connected to ITS400 sensor board of Imote2. More particularly, this work concerns the implementation of a localization algorithm based on the TDOA (Time Difference of Arrival) between the acquired signals by the microphones. This work can be divided into two parts. The first part is dedicated to the realization of an Imote2-based platform, which allows the acquisition of acoustic signals. In the second part, we have evaluated the performance of relative TOA (Time of Arrival) estimation algorithms, where CA-CFAR (Cell Averaging Constant False Alarm Rate) algorithm gave the best results.