Saleh O. Al-Jazzar

A scattering model based approach to NLOS mitigation in TOA location systems

We present a novel approach for reducing the effect of non-line-of-sight (NLOS) error that inhibits accurate location of wireless mobile stations (MSs). The location algorithm is developed based on the distribution of times of arrival (TOAs) generated from multipath scattering models that have been published in the literature. By matching the statistics of the measured TOAs of several multipath arrivals with those produced by the scattering models, estimates of the line-of-sight (LOS) TOAs between each base station (BS) and the MS are obtained. The LOS TOAs can then be used in any traditional TOA location algorithm. The algorithm shows a significant improvement in location accuracy for a TOA system in NLOS environment.

Scattering-Model-Based Methods for TOA Location in NLOS Environments

In this paper, we address methods of mitigating one of the major issues affecting wireless location accuracy in land mobile terrestrial environments: nonline-of-sight (NLOS) propagation. In order to improve location accuracy under such conditions, we propose a novel methodology for NLOS environments based on the use of scattering models to classify propagation environments. The scattering models allow modeling of the NLOS error so that the NLOS effect can be incorporated into a location algorithm. Through the use of the scattering models, we develop three novel location techniques based on the statistics of measured ranges via moment matching, the expectation maximization algorithm, and a Bayesian algorithm. Simulation results and discussion are given to illustrate the performance in typical NLOS environments. The results show that the algorithms provide improvement over traditional location algorithms

A Joint TOA/AOA Constrained Minimization Method for Locating Wireless Devices in Non-Line-of-Sight Environment

Non-line-of-sight (NLOS) propagation degrades the performance of wireless location systems. Thus, developing algorithms that are robust to NLOS is of great importance. This paper introduces a new location technique that utilizes time of arrival (TOA) and angle of arrival (AOA) measurements. In the proposed method, we assume the signal from the mobile station reaches each base station via one dominant scatterer. By including the scatterers coordinates as unknowns in a TOA/AOA-based cost function and imposing some equality and inequality constrains, the location of the mobile station (MS) is shown to significantly improve. The performance of the proposed algorithm is assessed and compared with that of existing algorithms through extensive simulations.

SVD-based joint azimuth/elevation estimation with automatic pairing

In this paper, a joint azimuth/elevation estimator with automatic pairing is developed. Two-dimensional (2-D) angle of arrival (AOA) estimation is useful in space processing systems and wireless location systems that employ AOA technology. The estimator makes use of a special setup of the received signal at an L-shaped antenna array element organized especially for the estimation process. The estimator is based on applying the singular value decomposition (SVD) algorithm to a cross-correlation matrix that is constructed from both arrays of the L-shaped structure. The proposed method avoids the computational burden of the complex pair-matching procedure. Simulations of the proposed method are shown to assess its performance.

A Joint TOA/AOA Constrained Minimization Method for Locating Wireless devices in Non-Line-of-Sight Environment

Non-line-of-sight (NLOS) propagation degrades the performance of wireless location systems. Thus, developing algorithms that are robust to NLOS considerations is of great importance. Based on time-of-arrival (TOA) and angle-of-arrival (AOA) measurements, this correspondence introduces a new approach, which consists of incorporating the coordinates of dominant scatterers as unknowns in the location algorithm. It is assumed that the first arriving path signal at each base station (BS) experiences a single dominant scatterer, but the BSs are allowed to have different dominant scatterers. Locating the mobile station is accomplished by means of a nonlinear optimization procedure under nonlinear constraints. Two algorithms are proposed: The first algorithm assumes that hybrid TOA/AOA measurements are available at three BSs. In the second algorithm, the AOA is assumed to be available at the serving BS only. The performance of the proposed algorithms is assessed and compared with that of existing algorithms through extensive simulations.

ESPRIT-based joint AOA/delay estimation for CDMA systems

In this paper, we present a joint delay/AOA estimator for CDMA systems in a multiuser environment. The algorithm is applicable to space-time channel estimation for space-time processing systems and to location systems that employ hybrid AOA/TOA technology. The estimator is based on a novel formulation of ESPRIT in which the delays and AOAs of each user can be estimated and automatically paired. The estimator avoids the computational burden of a matching, or pairing, procedure and does not require the use of a Fourier transform to aid the estimation of the delays. Further, the algorithm has lower computational complexity than other joint angle/delay estimators. An asymptotic first order error analysis as well as the Cramer-Rao lower bound (CRLB) are derived. Simulations are presented to show the performance of the estimator.

Analytical study on the effect of cochannel interference on partially coherent diversity systems

In this paper, we study the effect of cochannel interference (CCI) on the performance of partially coherent BPSK and QPSK in uncorrelated L-branch equal-gain combining systems. We consider a generalized propagation model wherein the desired and interfering signals undergo Nakagami-m or Rician fading with different amounts of fading severity. Further, the interfering signals are assumed to be asynchronous symbol timing with the desired signal, so that the effect of cross-signal intersymbol interference (ISI) is taken into account. Using a convergent Fourier series method, we derive extensive analytical results for the average bit error probability and the SNR gain penalty caused by the interference signals for different signal to-interference ratio levels. The numerical results presented in this paper demonstrate the system performance under very realistic propagation and detection conditions including CCI, carrier phase error recovery, cross-signal ISI, generalized fading channels, and AWGN. Hence our results are expected to be of significant practical use for such scenarios.

Simulation and Numerical Analysis of Wireless PSK Systems with Imperfect Carrier Phase Recovery

Abstract The bit error probability (BEP) of binary and quaternary PSK (BPSK and QPSK) signals over Rayleigh fading channel with imperfect carrier-phase recovery is derived. The channel is assumed to be slow and frequency-nonselective in which the received signal is constant over at least two symbol intervals. Numerical values for the average BEP are obtained by integrating the conditional BEP expression over the carrier-phase error distribution. The resultant integrands have only elementary functions, such as exponentials and algebraic power functions and can, therefore, be explicitly evaluated to any degree of accuracy. The accuracy of this approach is verified through proposing an efficient quazi-analytical simulation technique.

Enhancement of wireless positioning in outdoor suburban NLOS environment using hybrid-network-GPS systems

This article will introduce a method for locating mobile stations (MSs) in outdoor suburban non-line-of-sight (NLOS) environment. The measurements used to locate the MS are taken from three base stations and a satellite. Such a setup of measurements is named the hybrid-network-GPS system. The proposed method uses constraint nonlinear optimization to minimize the NLOS error. The problem is simplified to three independent nonlinear equations of three unknowns, then it is solved to find the MS location. Numerical simulations are introduced to assess the performance of the proposed method compared with other positioning algorithms.

Confidence Intervals Verification for Simulated Error Rate Performance of Wireless Communication System

In this paper, we derived an efficient simulation method to evaluate the error rate of wireless communication system. Coherent binary phase-shift keying system is considered with imperfect channel phase recovery. The results presented demonstrate the system performance under very realistic Nakagami-m fading and additive white Gaussian noise channel. On the other hand, the accuracy of the obtained results is verified through running the simulation under a good confidence interval reliability of 95 %. We see that as the number of simulation runs N increases, the simulated error rate becomes closer to the actual one and the confidence interval difference reduces. Hence our results are expected to be of significant practical use for such scenarios.