The main contribution of this paper is as follows: firstly, for analysing the performance of the ... more The main contribution of this paper is as follows: firstly, for analysing the performance of the tracking beam array (TBA), the adaptive procedure of designing an antenna array that tracks the maximum power source in which an adaptive algorithm based on Lagrange's formula provides the updated suboptimal weight vector at each snapshot to each subscriber is summarized. Secondly, for analysing the performance of the switching beam array (SBA), a simple way of selecting one narrow beam for each subscriber at each snapshot is presented. Thirdly, the two methods are compared in terms of the performances and required complexities. Since the signal environment considered in this paper is a code division multiple access (CDMA) mobile communication. The methods of achieving TBA and SBA provided in this paper are valid in the CDMA signal environment
Page 1. A Comparison of Tracking-Beam Arrays and Switching-Beam Arrays Operating in a CDMA Mobile... more Page 1. A Comparison of Tracking-Beam Arrays and Switching-Beam Arrays Operating in a CDMA Mobile Communication Channel Seungwon Clioi', Donghee Shim', and Tapan K. SarkaJ 'School of Electrical and Computcr ...
A new adaptive beamforming procedure is presented. The main contribution of the proposed techniqu... more A new adaptive beamforming procedure is presented. The main contribution of the proposed technique is in its simplicity without loss of accuracy. The computational load is about O(2N2+6N). It can further be reduced to O(4.5N) by approximating the autocovariance matrix with the instantaneous signal vector at each snapshot. The proposed technique is applied to the base station of a code division multiple access (CDMA) mobile communication system to demonstrate its performance in terms of the SINR (signal to interference+noise ratio), BER (bit-error-rate), and eventually the capacity of a given CDMA cell/sector
This paper presents the small-signal modeling, dynamic analysis, and control design of the asymme... more This paper presents the small-signal modeling, dynamic analysis, and control design of the asymmetrical half-bridge dc-dc converter that employs a clamp capacitor and a magnetizing inductor to accommodate pulsewidth-modulated operation with asymmetrical duty ratios. The circuit averaging technique is applied to extract the small-signal dynamics of the power stage, and a graphical loop-gain method is used to design the feedback compensation and analyze the closed-loop performance of the converter. The distinctive power-stage dynamics of the converter are addressed and design guidelines for voltage feedback compensation are established. The results of the control design and closed-loop analysis are substantiated by experiments using an experimental converter.
IEEE Transactions on Aerospace and Electronic Systems, 2001
This paper presents the theoretical and practical details involved in the control design and clos... more This paper presents the theoretical and practical details involved in the control design and closed-loop analysis of a step-down switched-capacitor DC-to-DC power converter. The state-space averaging technique is applied to extract the small-signal dynamics of the power stage, and a graphical loop gain method is used to design the feedback compensation and analyze the closed-loop performance of a switched-capacitor converter.
The problem of designing an adaptive antenna array as a countermeasure to the multipath fading wh... more The problem of designing an adaptive antenna array as a countermeasure to the multipath fading which occurs in land mobile communications is addressed. In order to approach the optimal weights of the antenna elements on a real-time basis, the conjugate gradient method (CGM) is applied to some practical procedures which have been contrived as realizable alternatives. The performance of the proposed technique is compared to that of the conventional recursive least square (RLS; Kalman) algorithm in terms of bit-error-rate (BER) and required computation time
This paper proposes two alternative techniques for the Direction-of-Arrival (DOA) estimation. Bot... more This paper proposes two alternative techniques for the Direction-of-Arrival (DOA) estimation. Both techniques utilize the respective modifications of the conjugate gradient method (CGM) for iteratively finding the weight vector which is orthogonal to the signal subspace. In the first method, an eigenvector corresponding to the smallest eigenvalue is computed by minimizing the Rayleigh quotient of the full complex-valued autocovariance matrix.
When trying to analyze a complex communication system, scientists often apply concepts from stoch... more When trying to analyze a complex communication system, scientists often apply concepts from stochastic modeling and analysis to obtain a description of the system, frequently assuming that this will supplement our knowledge and improve our understanding. The philosophy is to obtain a result that would occur on the average, when this system is working under normal conditions. However, we must consider the fact that the introduction of probability in communication-system analysis often involves invoking certain assumptions and additional information about the system, which may not be valid. Hence, under these circumstances one may obtain a result that may not be commensurate with the conceived communication system. The objective of this paper is to highlight the basic assumptions that are invariably associated with the signal analysis in a system using stochastic analysis, and the introduction of probabilistic methods. Surprisingly, in many cases, analysis using stochastic methods may provide results equivalent to those obtained using deterministic methods. Examples are presented to illustrate our approach, and to explain the basic assumptions and formulate the mathematical framework associated with a stochastic analysis. We also demonstrate the equivalence between a random and a deterministic process, and under what conditions they approach the Cramer-Rao bound. Analysis using stochastic models to describe a system may be superior to a deterministic description. However, such a characterization comes with a large cost: namely, one must have more definitive knowledge about the system, knowledge that is often unavailable. For convenience, with the application of a random model, the concepts of stationarity and ergodicity are used to simplify the mathematical analysis of measured data. It is shown that the introduction of ergodicity in probability is similar to a deterministic analysis of a single waveform, and, in both cases, characterizes the entire underlying mathematical agenda. An example is presented to illustrate the salient features of an ergodic process as opposed to a deterministic process. It is seen that for practical problems, it might be easier and more relevant to introduce a deterministic model and to then carry out a stochastic analysis. However,- this may not be practical, since the underlying ensemble is not available nor are its probability density functions. Moreover a deterministic solution may present the best solution for a given data set, whereas the stochastic approach yields an "average" solution for all the waveforms in the ensemble. Hence, the stochastic solution may not be the desired solution for the given data set. However, when accurate statistics are available, a better solution may be obtained using probabilistic methods.
The main contribution of this paper is as follows: firstly, for analysing the performance of the ... more The main contribution of this paper is as follows: firstly, for analysing the performance of the tracking beam array (TBA), the adaptive procedure of designing an antenna array that tracks the maximum power source in which an adaptive algorithm based on Lagrange's formula provides the updated suboptimal weight vector at each snapshot to each subscriber is summarized. Secondly, for analysing the performance of the switching beam array (SBA), a simple way of selecting one narrow beam for each subscriber at each snapshot is presented. Thirdly, the two methods are compared in terms of the performances and required complexities. Since the signal environment considered in this paper is a code division multiple access (CDMA) mobile communication. The methods of achieving TBA and SBA provided in this paper are valid in the CDMA signal environment
Page 1. A Comparison of Tracking-Beam Arrays and Switching-Beam Arrays Operating in a CDMA Mobile... more Page 1. A Comparison of Tracking-Beam Arrays and Switching-Beam Arrays Operating in a CDMA Mobile Communication Channel Seungwon Clioi', Donghee Shim', and Tapan K. SarkaJ 'School of Electrical and Computcr ...
A new adaptive beamforming procedure is presented. The main contribution of the proposed techniqu... more A new adaptive beamforming procedure is presented. The main contribution of the proposed technique is in its simplicity without loss of accuracy. The computational load is about O(2N2+6N). It can further be reduced to O(4.5N) by approximating the autocovariance matrix with the instantaneous signal vector at each snapshot. The proposed technique is applied to the base station of a code division multiple access (CDMA) mobile communication system to demonstrate its performance in terms of the SINR (signal to interference+noise ratio), BER (bit-error-rate), and eventually the capacity of a given CDMA cell/sector
This paper presents the small-signal modeling, dynamic analysis, and control design of the asymme... more This paper presents the small-signal modeling, dynamic analysis, and control design of the asymmetrical half-bridge dc-dc converter that employs a clamp capacitor and a magnetizing inductor to accommodate pulsewidth-modulated operation with asymmetrical duty ratios. The circuit averaging technique is applied to extract the small-signal dynamics of the power stage, and a graphical loop-gain method is used to design the feedback compensation and analyze the closed-loop performance of the converter. The distinctive power-stage dynamics of the converter are addressed and design guidelines for voltage feedback compensation are established. The results of the control design and closed-loop analysis are substantiated by experiments using an experimental converter.
IEEE Transactions on Aerospace and Electronic Systems, 2001
This paper presents the theoretical and practical details involved in the control design and clos... more This paper presents the theoretical and practical details involved in the control design and closed-loop analysis of a step-down switched-capacitor DC-to-DC power converter. The state-space averaging technique is applied to extract the small-signal dynamics of the power stage, and a graphical loop gain method is used to design the feedback compensation and analyze the closed-loop performance of a switched-capacitor converter.
The problem of designing an adaptive antenna array as a countermeasure to the multipath fading wh... more The problem of designing an adaptive antenna array as a countermeasure to the multipath fading which occurs in land mobile communications is addressed. In order to approach the optimal weights of the antenna elements on a real-time basis, the conjugate gradient method (CGM) is applied to some practical procedures which have been contrived as realizable alternatives. The performance of the proposed technique is compared to that of the conventional recursive least square (RLS; Kalman) algorithm in terms of bit-error-rate (BER) and required computation time
This paper proposes two alternative techniques for the Direction-of-Arrival (DOA) estimation. Bot... more This paper proposes two alternative techniques for the Direction-of-Arrival (DOA) estimation. Both techniques utilize the respective modifications of the conjugate gradient method (CGM) for iteratively finding the weight vector which is orthogonal to the signal subspace. In the first method, an eigenvector corresponding to the smallest eigenvalue is computed by minimizing the Rayleigh quotient of the full complex-valued autocovariance matrix.
When trying to analyze a complex communication system, scientists often apply concepts from stoch... more When trying to analyze a complex communication system, scientists often apply concepts from stochastic modeling and analysis to obtain a description of the system, frequently assuming that this will supplement our knowledge and improve our understanding. The philosophy is to obtain a result that would occur on the average, when this system is working under normal conditions. However, we must consider the fact that the introduction of probability in communication-system analysis often involves invoking certain assumptions and additional information about the system, which may not be valid. Hence, under these circumstances one may obtain a result that may not be commensurate with the conceived communication system. The objective of this paper is to highlight the basic assumptions that are invariably associated with the signal analysis in a system using stochastic analysis, and the introduction of probabilistic methods. Surprisingly, in many cases, analysis using stochastic methods may provide results equivalent to those obtained using deterministic methods. Examples are presented to illustrate our approach, and to explain the basic assumptions and formulate the mathematical framework associated with a stochastic analysis. We also demonstrate the equivalence between a random and a deterministic process, and under what conditions they approach the Cramer-Rao bound. Analysis using stochastic models to describe a system may be superior to a deterministic description. However, such a characterization comes with a large cost: namely, one must have more definitive knowledge about the system, knowledge that is often unavailable. For convenience, with the application of a random model, the concepts of stationarity and ergodicity are used to simplify the mathematical analysis of measured data. It is shown that the introduction of ergodicity in probability is similar to a deterministic analysis of a single waveform, and, in both cases, characterizes the entire underlying mathematical agenda. An example is presented to illustrate the salient features of an ergodic process as opposed to a deterministic process. It is seen that for practical problems, it might be easier and more relevant to introduce a deterministic model and to then carry out a stochastic analysis. However,- this may not be practical, since the underlying ensemble is not available nor are its probability density functions. Moreover a deterministic solution may present the best solution for a given data set, whereas the stochastic approach yields an "average" solution for all the waveforms in the ensemble. Hence, the stochastic solution may not be the desired solution for the given data set. However, when accurate statistics are available, a better solution may be obtained using probabilistic methods.
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