The Experts below are selected from a list of 11700 Experts worldwide ranked by ideXlab platform

T H Meng - One of the best experts on this subject based on the ideXlab platform.

  • iterative power control for imperfect successive interference Cancellation
    IEEE Transactions on Wireless Communications, 2005
    Co-Authors: A. Agrawal, Jeffrey G Andrews, J M Cioffi, T H Meng
    Abstract:

    Successive interference Cancellation (SIC) is a technique for increasing the capacity of cellular code-division multiple-access (CDMA) systems. To be successful, SIC systems require a specific distribution of the users' received powers, especially in the inevitable event of imperfect interference Cancellation. This apparent complication of standard CDMA power control has been frequently cited as a major drawback of SIC. In this paper, it is shown that surprisingly, these "complications" come with no additional complexity. It is shown that 1-bit UP/DOWN power control-like that used in commercial systems-monotonically converges to the optimal power distribution for SIC with Cancellation Error. The convergence is proven to within a discrete step-size in both signal-to-noise plus interference ratio and power. Additionally, the algorithm is applicable to multipath and fading channels and can overcome channel estimation Error with a standard outer power control loop.

Ian Postlethwaite - One of the best experts on this subject based on the ideXlab platform.

  • nonlinear robust performance analysis using complex step gradient approximation
    Automatica, 2006
    Co-Authors: Jongrae Kim, Declan G Bates, Ian Postlethwaite
    Abstract:

    In this paper, the complex-step method is applied in the setting of numerical optimisation problems involving dynamical systems modelled as nonlinear differential equations. The main advantage of the complex-step method for gradient approximation is that it entails no subtractive Cancellation Error, and therefore the truncation Error can be made arbitrarily (to machine precision) small. The method is applied to two robust performance analysis problems. The accuracy and convergence rate of the solutions computed using the proposed approach are seen to be significantly better than those achieved using standard gradient approximation methods.

  • complex step gradient approximation for robustness analysis of nonlinear systems
    IFAC Proceedings Volumes, 2005
    Co-Authors: Jongrae Kim, Declan G Bates, Ian Postlethwaite
    Abstract:

    Abstract In this paper, the complex-step perturbation method is extended to the setting of optimisation problems involving dynamical systems modelled as nonlinear differential equations. The main advantage of the complex-step method for gradient approximation is that it entails no subtraction Cancellation Error, and therefore the truncation Error can be made arbitrarily small. The method is applied to two robust performance analysis problems and is shown to provide more accurate solutions and improved convergence times when compared with standard finite difference-based approaches.

A. Agrawal - One of the best experts on this subject based on the ideXlab platform.

  • iterative power control for imperfect successive interference Cancellation
    IEEE Transactions on Wireless Communications, 2005
    Co-Authors: A. Agrawal, Jeffrey G Andrews, J M Cioffi, T H Meng
    Abstract:

    Successive interference Cancellation (SIC) is a technique for increasing the capacity of cellular code-division multiple-access (CDMA) systems. To be successful, SIC systems require a specific distribution of the users' received powers, especially in the inevitable event of imperfect interference Cancellation. This apparent complication of standard CDMA power control has been frequently cited as a major drawback of SIC. In this paper, it is shown that surprisingly, these "complications" come with no additional complexity. It is shown that 1-bit UP/DOWN power control-like that used in commercial systems-monotonically converges to the optimal power distribution for SIC with Cancellation Error. The convergence is proven to within a discrete step-size in both signal-to-noise plus interference ratio and power. Additionally, the algorithm is applicable to multipath and fading channels and can overcome channel estimation Error with a standard outer power control loop.

Boashash Boualem - One of the best experts on this subject based on the ideXlab platform.

  • Robust estimation of highly-varying nonlinear instantaneous frequency of monocomponent signals using a lower-order complex-time distribution
    'Elsevier BV', 2013
    Co-Authors: Omidvarnia Amir, Azemi Ghasem, O' Toole, John M., Boashash Boualem
    Abstract:

    This paper proposes an approach for robust estimation of highly-varying nonlinear instantaneous frequency (IF) in monocomponent nonstationary signals. The proposed method is based on a lower order complex-time distribution (CTD), derived by using the idea of complex-time differentiation of the instantaneous phase. Unlike other existing TFDs in the same framework, the proposed TFD is an order-free distribution which alleviates the subtractive Cancellation Error in IF estimation. The approach is applied to highly nonstationary monocomponent signals. Performance of the numerical implementation is compared with three existing IF estimation methods using three simulated signals. Noise analysis is also performed to evaluate the robustness of the method in presenfdece of additive noise at signal to noise ratio (SNR) varying from -10 dB to 20 dB. Results show that the proposed method outperforms the other methods at lower SNR and works reasonably well for the noiseless case. (C) 2013 Elsevier B.V. All rights reserved

Boashash B. - One of the best experts on this subject based on the ideXlab platform.

  • Robust estimation of highly-varying nonlinear instantaneous frequency of monocomponent signals using a lower-order complex-time distribution
    'Elsevier BV', 2013
    Co-Authors: Omidvarnia A., Azemi G., O'toole J.m., Boashash B.
    Abstract:

    This paper presents a robust method for estimating highly-changing nonlinear IFs in monocomponent signals using a lower order CTD based on the general concept of complex-time argument differentiation. (Additional details can be found in the comprehensive book on Time-Frequency Signal Analysis and Processing (see http://www.elsevier.com/locate/isbn/0080443354). In addition, the most recent upgrade of the original software package that calculates Time-Frequency Distributions and Instantaneous Frequency estimators can be downloaded from the web site: www.time-frequency.net. This was the first software developed in the field, and it was first released publicly in 1987 at the 1st ISSPA conference held in Brisbane, Australia, and then continuously updated).This paper proposes an approach for robust estimation of highly-varying nonlinear instantaneous frequency (IF) in monocomponent nonstationary signals. The proposed method is based on a lower order complex-time distribution (CTD), derived by using the idea of complex-time differentiation of the instantaneous phase. Unlike other existing TFDs in the same framework, the proposed TFD is an order-free distribution which alleviates the subtractive Cancellation Error in IF estimation. The approach is applied to highly nonstationary monocomponent signals. Performance of the numerical implementation is compared with three existing IF estimation methods using three simulated signals. Noise analysis is also performed to evaluate the robustness of the method in presenfdece of additive noise at signal to noise ratio (SNR) varying from −10 dB to 20 dB. Results show that the proposed method outperforms the other methods at lower SNR and works reasonably well for the noiseless case