DoA estimation with cell searching for mobile relay stations with uniform circular array.
ABSTRACT In this paper, a Direction-of-Arrival (DoA) estimation scheme with cell searching is proposed for a mobile relay station (MRS) with uniform circular array (UCA) at handover region. The proposed scheme of cell searching and DoA estimation for the MRS with UCA is robust even when there exist symbol timing offsets (STOs). Compared with the previous scheme, the proposed scheme can reduce computational complexity and processing time for cell searching and DoA estimation. Simulation results are included to verify the performance of the proposed scheme under Mobile WiMAX environment.
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ABSTRACT: Relaying and cooperation have re-emerged as important research topics in wireless communication over the past half-decade. Although multihop relaying for coverage extension in wireless networks is an old concept, it became practical only recently. Nowhere is this better illustrated than in the IEEE 802.16 working group, which has devoted a task group to incorporating relay capabilities in the foundation of mobile WiMAX-IEEE 802.16e-2005. Currently, this task group is in the process of finishing IEEE 802.16j, the multihop relay specification for 802.16. This amendment will be fully compatible with 802.16e-2005 mobile and subscriber stations, but a BS specific to 802.16j will be required for relays to operate. This article presents an introduction to the upcoming IEEE 802.16j amendment and provides insight about the obstacles that practical system designers face when incorporating relaying into a wireless broadband network.IEEE Communications Magazine 02/2009; · 4.46 Impact Factor
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ABSTRACT: A metamaterial paradigm for achieving an efficient, electrically small antenna is introduced. Spherical shells of homogenous, isotropic negative permittivity (ENG) material are designed to create electrically small resonant systems for several antennas: an infinitesimal electric dipole, a very short center-fed cylindrical electric dipole, and a very short coaxially-fed electric monopole over an infinite ground plane. Analytical and numerical models demonstrate that a properly designed ENG shell provides a distributed inductive element resonantly matched to these highly capacitive electrically small antennas, i.e., an ENG shell can be designed to produce an electrically small system with a zero input reactance and an input resistance that is matched to a specified source resistance leading to overall efficiencies approaching unity. Losses and dispersion characteristics of the ENG materials are also included in the analytical models. Finite element numerical models of the various antenna-ENG shell systems are developed and used to predict their input impedances. These electrically small antenna-ENG shell systems with idealized dispersionless ENG material properties are shown to be very efficient and to have fractional bandwidths above the values associated with the Chu limit for the quality factor without any degradation in the radiation patterns of the antennas. Introducing dispersion and losses into the analytical models, the resulting bandwidths are shown to be reduced significantly, but remain slightly above (below) the corresponding Chu-based value for an energy-based limiting (Drude) dispersion model of the permittivity of the ENG shell.IEEE Transactions on Antennas and Propagation 08/2006; · 2.46 Impact Factor
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ABSTRACT: The problem of 2D angle estimation (azimuth and elevation) of multiple plane waves incident on a uniform circular array (UCA) of antennas is considered. Two eigenstructure-based estimation algorithms that operate in beamspace and employ phase mode excitation-based beamformers have been developed. The first, UCA-RB-MUSIC, is a beamspace version of MUSIC that offers numerous advantages over element space operation, including reduced computation, as subspace estimates are obtained via real-valued eigendecompositions, enhanced performance in correlated source scenarios due to the attendant forward-backward averaging effect, and the applicability of Root-MUSIC. The second, UCA-ESPRIT, represents a significant advance in the area of 2D angle estimation. It is a novel closed-form algorithm that provides automatically paired source azimuth and elevation estimates. With UCA-ESPRIT, the eigenvalues of a matrix have the form μ<sub>i</sub>=sin θ<sub>i</sub>e<sup>jφ(i/), where θ</sup>sub i/ and φ<sub>i</sub> are the elevation and azimuth angles, respectively. Expensive search procedures being thus avoided, UCA-ESPRIT is superior to existing 2D angle estimation algorithms with respect to computational complexity. Finally, asymptotic expressions for the variances of the element space MUSIC and UCA-RB-MUSIC estimators for the 2D scenario have been derived. Results of simulations that compare UCA-RB-MUSIC and UCA-ESPRIT and also validate the theoretical performance expressions are presentedIEEE Transactions on Signal Processing 10/1994; · 3.20 Impact Factor