A. Le.e Swindlehurst

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We consider in this paper the problem of extending the ESPRIT algorithm for multiple source, co-channel direction nding to the two-dimensional case (e.g., azimuth and elevation angle estimation). Two algorithms are presented, one based on the optimal (minimum variance) subspace tting formulation of ESPRIT, and the other based on an approximation to it. The(More)
The performance of a mobile MIMO-OFDM system depends on the ability of the system to accurately account for the effects of the frequency-selective time-varying channel at every symbol time and at every frequency subcarrier. In this paper, a vector formulation of the Cramer-Rao bound (CRB) for biased estimators and for functions of parameters is used to find(More)
We compare the performance of several algorithms for signal separation based on actual mobile cellular radio data. The data were collected by base stations in two different environments: using an eight element linear array on a hillside overlooking a suburban area, and using a four element square array at the top of a ten story building in a dense urban(More)
The primary issue in downlink beamforming for wireless communications is how to balance the need for high received signal power for each user against the interference produced by the signal at other points in the network. In this paper, we describe several approaches to this problem: channel inversion, regularized channel inversion, vector modulo(More)
The majority of algorithms developed for the narrowband direction of arrival (DOA) estimation problem rely on an eigenvalue decomposition (EVD) to determine both the number of signals and their respective DOAs. An alternative algorithm is presented that solves both the DOA detection and estimation problems without resorting to an EVD. The algorithm is shown(More)
The performance of DF-based beamformers is seriously degraded in situations where the array is imprecisely calibrated, or when the spatial coherence of the signal wavefronts is perturbed. When the calibration errors or perturbation may be characterized by a set of parameters drawn from a known Gaussian distribution , a maximum a posteriori (MAP) estimator(More)
Herein, we investigate the optimal deployment of an unmanned aerial vehicle (UAV) in a wireless relay communication system. The optimal UAV position is found by maximizing the average data rate, while at the same time keeping the symbol error rate (SER) below a certain threshold. We derive a closed-form expression for the average data rate in a fixed(More)
Conventional methods for signal copy require one to estimate the directions of arrival (DOA's) of the signals prior to computing the weight vectors. Blind copy algorithms alleviate the need for DOA estimation (and hence the need for array calibration data) by exploiting the temporal rather than spatial structure of the signals, but they converge slowly in(More)