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ABSTRACT: An efficient feedforward blind carrier frequency offset (CFO) estimator for orthogonal frequency division multiplexing (OFDM) systems with general symbol constellation is presented. The proposed estimator requires only one OFDM symbol period to blindly and accurately estimate the CFO in Gaussian and multipath fading channels.
Electronics Letters 02/2008; · 0.96 Impact Factor
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R.M. Shubair
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ABSTRACT: The least mean squares (LMS) algorithm is a simple adaptive beamforming algorithm that is well suited for continuous transmission systems. The LMS algorithm converges slowly when compared with other complicated algorithms, such as recursive least squares (RLS) (Shubair, R.M. and Merri, A., 2005). On the other hand, the sample matrix inversion (SMI) algorithm has a fast convergence behavior. However, because its speedy convergence is achieved through the use of matrix inversion, the SMI algorithm is computationally intensive. Moreover, the SMI algorithm has a block adaptive approach for which it is required that the signal environment does not undergo significant change during the course of block acquisition. The paper develops an algorithm for robust adaptive beamforming by combining the attributes of the LMS algorithm and SMI algorithm. This new algorithm uses the LMS algorithm, which is simple to implement and not computationally intensive, but with SMI initialization in order to ensure fast convergence. Numerical results verify the improved convergence, accuracy, and computational efficiency of the combined LMS/SMI algorithm.
Antennas and Propagation Society International Symposium, 2005 IEEE; 08/2005
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ABSTRACT: High-resolution signal processing using sensor arrays to estimate the directions of unknown correlated signals in multipath environments is associated with high computational complexity. This paper proposes a computationally efficient direction of arrival (DOA) estimation algorithm. The algorithm is based on two stages of detection: a first stage for discriminating uncorrelated signals and a second stage for resolving the directions of arrival of correlated signals using covariance differencing and iterative spatial smoothing. Simulation results show that the proposed algorithm operates at a much lower computational cost compared to standard methods.
Circuits and Systems, 2005. ISCAS 2005. IEEE International Symposium on; 06/2005
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ABSTRACT: This paper proposes a hybrid algorithm for improved adaptive beamforming by combining the attributes of LMS and SMI algorithms. The proposed algorithm uses the LMS algorithm, which simple to implement and not computationally intensive, with SMI initialization in order to ensure fast convergence. Numerical results are presented to verify the improved convergence, accuracy, and computational efficiency of the proposed hybrid LMS/SMI algorithm.
Wireless and Optical Communications Networks, 2005. WOCN 2005. Second IFIP International Conference on; 04/2005
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ABSTRACT: In this paper we have presented the theory and analyzed the performance of the SMI adaptive beamforming algorithm for smart antenna systems. The SMI algorithm is based on block-data weight adaptation. Simulations results obtained show that SMI algorithm is able to iteratively update the array weights to force deep nulls in the directions of the interferes, and achieve a maximum in the direction of the desired signal. The resulting beampattern is the same throughout all iterations since a solution for the optimal weights is independently computed for each data block. The SMI algorithm was found to converge almost immediately during the first data block with a small amount of residual error
Antennas and Propagation Society International Symposium, 2005 IEEE; 02/2005
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International Symposium on Circuits and Systems (ISCAS 2005), 23-26 May 2005, Kobe, Japan; 01/2005
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ABSTRACT: This paper presents a performance evaluation of robust algorithms for direction finding and adaptive beamforming used in the design of smart antenna systems. A simulation tool with a graphical user interface which implements these algorithms is developed. Results of numerical simulation are used to design smart antennas systems with optimal performance.
Circuits and Systems, 2004. MWSCAS '04. The 2004 47th Midwest Symposium on; 08/2004
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ABSTRACT: A computationally efficient direction of arrival (DOA) estimation algorithm using a linear array of equispaced sensors is proposed for a multipath environment with unknown correlated signals. The algorithm comprises two stages: a first stage for discriminating uncorrelated signals, and a second stage for resolving the directions of arrival of the correlated signals using covariance differencing and iterative spatial smoothing. Simulation results show that the proposed algorithm operates at a much lower computational cost compared to standard methods.
Electronics Letters 08/2004; · 0.96 Impact Factor
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ABSTRACT: This paper presented a versatile smart antenna simulation tool which implements both direction finding and adaptive beamforming algorithms. The developed tool can be used for modelling of adaptive antenna arrays to improve and accelerate the design of wireless networks. The developed tool can also be used for computer-aided learning of modern communication systems that utilize smart antennas.
Antennas and Propagation Society International Symposium, 2004. IEEE; 07/2004
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ABSTRACT: A performance study of LMS adaptive beamformers has been carried out by investigating the effect of parameters related to both the beamforming array and signal environment. These parameters include number of beamformer array elements and their spacing, as well as the number of users and their angular separation. The performance study is essential for an optimal design of smart antenna systems utilizing LMS beamformers.
Antennas and Propagation Society International Symposium, 2004. IEEE; 07/2004
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ABSTRACT: Adaptive beamforming is a key feature of smart antennas that leads to interference mitigation and capacity increase of wireless networks. This paper presents a performance evaluation of the LMS algorithm that is used as an adaptive beamforming technique in smart antennas. This performance evaluation is carried out with respect to the antenna array size in terms of the number of elements forming this array as well as their physical spacing. Also the signal environment parameters are analyzed in terms of the number of signals incident on the antenna array and their angular separation.
Circuits and Systems, 2003 IEEE 46th Midwest Symposium on; 01/2004
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ABSTRACT: This paper presents a simulation tool for direction-of-arrival (DOA) estimation in adaptive signal processing arrays. The tool implements the multiple signal classification (MUSIC) DOA algorithm. A user-friendly graphical user interface (GUI) is also developed. In addition to its usefulness in the design and analysis of adaptive signal processing arrays, the tool can also be used for computer-aided learning of modem communication systems utilizing smart antennas. To demonstrate the versatility and accuracy of the developed tool, it is used to carry out a detailed performance analysis of DOA estimation using MUSIC. This includes investigating the effect of the number of mobile users and their spatial distribution, the number of array elements and their spacing, and the number of signal snapshots.
Electronics, Circuits and Systems, 2003. ICECS 2003. Proceedings of the 2003 10th IEEE International Conference on; 01/2004
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ABSTRACT: Adaptive antenna arrays have been widely adopted in third-generation (3G) mobile systems due to their capability of increasing the coverage range and capacity of base stations by directing beam patterns towards the desired signals and -patterns towards the interferers. A key to such capability is the use of Direction-of-Arrival (DOA) techniques. This paper evaluates and compares the performance of three high-resolution DOA algorithms. In particular, the paper investigates the boundaries within which the performance of the algorithms is considered acceptable.
Electronics, Circuits and Systems, 2003. ICECS 2003. Proceedings of the 2003 10th IEEE International Conference on; 01/2004
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ABSTRACT: This paper presents an efficient implementation of space-time coding for broadband wireless communications. A user-friendly menu-driven space time (ST) trellis code simulator with a graphical user interface (GUI) is developed. The simulator is used to predict the improved performance and diversity gains of a ST coding system through a number of parameters including type of trellis codes and channel fading. Results are presented to demonstrate the versatility of the developed simulator for predicting the performance of a ST coding system under different coding and channel conditions.
Electronics, Circuits and Systems, 2003. ICECS 2003. Proceedings of the 2003 10th IEEE International Conference on; 01/2004
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ABSTRACT: High-resolution signal processing for broadband wireless communications employing smart antenna arrays is associated with high costs, both in terms of hardware and computational complexity. This paper presents a performance evaluation of robust and high-resolution direction-of-arrival (DOA) estimation algorithms used in the design of smart antenna systems. A comparative study is carried out by evaluating the performance of these DOA algorithms for a set of input parameters that include the size of the sensor array, number and angular separation of incident signals from the mobile terminals, as well as noise characteristics of the mobile communication channel. Performance improvement in DOA estimation is demonstrated for certain range of input parameters and the results of the numerical experiments are used to set the criteria for optimal performance of the smart antenna system.
3G Mobile Communication Technologies, 2003. 3G 2003. 4th International Conference on (Conf. Publ. No. 494); 07/2003
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ABSTRACT: This paper presents an efficient implementation of space-time coding for broadband wireless communications. A user-friendly menu-driven space time (ST) trellis coding simulator with a graphical user interface (GUI) is developed. The simulator is used to predict the improved performance and diversity gains of a ST coding system through a number of parameters including type of trellis codes and channel fading. Results are presented to demonstrate the versatility of the developed simulator for predicting the performance of a ST coding system under different coding and channel conditions.
3G Mobile Communication Technologies, 2003. 3G 2003. 4th International Conference on (Conf. Publ. No. 494); 07/2003
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ABSTRACT: A combination of analytical and numerical techniques is used to develop an efficient and robust computer-aided toolbox that allows for an interactive simulation and visualization of guided wave propagation in dielectric and optical waveguides. The toolbox has been developed using the MATLAB programming language, exploiting its powerful graphical features that allow for both the 2D and 3D propagation patterns to be interactively displayed along the waveguide structure. A user-friendly graphical interface is also developed to ease the use of the toolbox
Antennas and Propagation Society International Symposium, 2001. IEEE; 02/2001
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R.M. Shubair
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ABSTRACT: This paper presents a technique for a rapidly convergent computation of the periodic Green's function in multilayered dielectric media. The technique is based on a hybrid spectral/spatial summation formula with optimized complex images. In comparison with other techniques that are applicable to the free-space periodic Green's function, our technique can be easily used for an efficient and accurate computation of the periodic Green's function in multilayered dielectric media. This means that the developed technique is of potential importance as it can be applied to a wide class of problems where the modeling of periodic structures is required
Antennas and Propagation Society International Symposium, 1999. IEEE; 09/1999
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ABSTRACT: This paper derives a convenient closed-form expression for the
input impedance of a vertical antenna above a dielectric half-space. The
expression is obtained from the induced electromotive force (EMF) method
using a complex-image spatial Green's function. It is found that the
effect of the dielectric half-space can be modeled by a short image
array of three to five complex image antennas. Numerical results verify
the accuracy and convenience of the method for a vertical antenna at any
height above a dielectric half-space with and without loss
IEEE Transactions on Antennas and Propagation 01/1994; · 2.15 Impact Factor
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ABSTRACT: An efficient technique is developed to solve the important problem
of vertical antennas located above and penetrating the interface between
contiguous dielectric half-spaces. It begins by deriving the spectral
expressions of the vector and scalar potential Green functions in terms
of the TM wave spectral transmission coefficient. The complex image
technique is used to derive simple, accurate, and rapidly convergent
expressions of the full-wave spatial Green functions. The spatial Green
functions are used in the moment method to model vertical thin-wire
antennas residing above the penetrating the interface separating the
contiguous dielectric half-spaces with and without loss
IEEE Transactions on Antennas and Propagation 07/1993; · 2.15 Impact Factor
