The Experts below are selected from a list of 2439 Experts worldwide ranked by ideXlab platform
Norman S. Kopeika - One of the best experts on this subject based on the ideXlab platform.
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Adaptive Suboptimum detection of an optical pulse-position-modulation signal with a detection matrix and centroid tracking
Journal of the Optical Society of America A, 1998Co-Authors: Shlomi Arnon, Norman S. KopeikaAbstract:In some applications of optical communication systems, such as satellite optical communication and atmospheric optical communication, the optical beam wanders on the detector surface as a result of vibration and turbulence effects, respectively. The wandering of the beam degrades the communication system performance. In this research, we derive a mathematical model of an optical communication system with a detection matrix to improve the system performance for direct-detection pulse-position modulation. We include a centroid tracker in the communication system model. The centroid tracker tracks the center of the beam. Using the position of the beam center and an a priori model of the beam spreading, we estimate the optical power on each pixel (element) in the detection matrix. Using knowledge of the amplitudes of signal and noise in each pixel, we tune adaptively and separately the gain of each individual pixel in the detection matrix for communication signals. Tuning the gain is based on the mathematical model derived in this research. This model is defined as suboptimal, owing to some approximations in the development and is a Suboptimum solution to the optimization problem of n multiplied by m free variables, where n, m are the dimensions of the detection matrix. Comparison is made between the adaptive Suboptimum model and the standard model. From the mathematical analysis and the results of the comparison it is clear that this model significantly improves communication system performance.
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Adaptive Suboptimum detection of optical PPM signal with detection matrix and centroid tracking
Photonics for Space Environments V, 1997Co-Authors: Arnon Shlomi, Norman S. KopeikaAbstract:In some applications of optical communication systems, such as satellite optical communication and atmospheric optical communication, the optical beam wanders on the detector surface due to vibration and turbulence effects, respectively. The wandering of the beam degrades the communication system performance. In this research, we derive a mathematical model of an optical communication system with a detection matrix to improve the system performance for direct detection pulse position modulation (PPM) We include a centroid tracker in the communication system model. The centroid tracker tracks the center of the beam. Using the position of beam center and an apriori model of beam spreading we estimate the optical power on each pixel (element) in the detection matrix. Based on knowledge of the amplitudes of signal and noise in each pixel, we tune adaptively and separately the gain of each individual pixel in the detection matrix for communication signals. Tuning the gain is based on the mathematical model derived in this research. This model is defined as suboptimal due to some approximations in the development and is a Suboptimum solution to the optimization problem of n multiplied by m free variables, where U,mare the dimensions of the detection matrix. Comparison is made between the adaptive Suboptimum model and the standard model. From the mathematical analysis and the results of the comparison it is clear that this model improves significantly communication system performance.
Kah Chan Teh - One of the best experts on this subject based on the ideXlab platform.
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performance analysis of a Suboptimum fast frequencyhopped m ary frequency shift keying maximumlikelihood receiver over rician fading channels with composite effects of partial band noise jamming and multitone jamming
Iet Communications, 2012Co-Authors: Kah Chan TehAbstract:Bit-error rate (BER) expressions of a Suboptimum maximum-likelihood (ML) receiver with the composite effect of partial-band noise jamming and multitone jamming are derived for fast frequency-hopped systems employing M-ary frequency-shift-keying modulation over Rician-fading channels. These BER expressions can be used to study the system performance under Rayleigh fading as a special case. Owing to the fact that the computation of the logarithm of the modified Bessel function is non-linear in nature, one of the existing approximations is required to derive the BER expressions for the analysed system. A Suboptimum ML receiver structure is therefore proposed and analysed. The analytical results are compared with simulation results. Under various jamming and fading conditions, the proposed Suboptimum ML receiver is found to be able to suppress interference effectively.
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performance study of Suboptimum maximum likelihood receivers for ffh mfsk systems with multitone jamming over fading channels
IEEE Transactions on Vehicular Technology, 2005Co-Authors: Yang Han, Kah Chan TehAbstract:We derive two Suboptimum maximum-likelihood (ML) receivers for fast frequency-hopped M-ary frequency-shift-keying (FSK) spread-spectrum (SS) communication systems. These two receiver structures attempt to countermeasure the effects of the worst case multitone jamming (MTJ) and additive white Gaussian noise over Rayleigh- and Rician-fading channels, respectively. In addition, analytical bit-error-rate (BER) expressions for the two proposed Suboptimum structures are derived and validated by simulation results. Performance comparisons among various receivers show that the proposed Suboptimum receivers significantly outperform the other existing receivers over fading channels. The optimum diversity level of the Suboptimum ML receiver for the Rayleigh-fading case is found to be higher than that of the Rician-fading case. In addition, the proposed Suboptimum ML receivers with optimum diversity levels can effectively remove the effect of MTJ, even under very low signal-to-jamming ratio conditions.
R. Tafazolli - One of the best experts on this subject based on the ideXlab platform.
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Low complex interference cancellation via modified Suboptimum search algorithm and reduced rank linear detection for mobile uplink
2005 IEEE 61st Vehicular Technology Conference, 2005Co-Authors: M. Mozaffaripour, R. TafazolliAbstract:A low complex interference cancellation via modified Suboptimum search algorithm in conjunction with a primary stage of reduced rank linear (RRL) multiuser detector for the mobile uplink is proposed. Initial stage is improved through mathematical analysis via Gershgorin algorithm in linear algebra and RRLG detector is introduced. The complexity of the initial stage is evaluated and compared to the recently reported low-complex Fourier interference cancellation method. Depending on the value of the spreading factor of the active users in system, RRLG outperforms the Fourier algorithm, in terms of complexity. The structure of the RRLG method and the Suboptimum search algorithm are well suited together and makes them collaboratively work without encountering a high level of complexity. Considering the power profile of the users in the Suboptimum search algorithm leaded to even less complexity, yet keeping the performance almost the same. The performance of the structure is obtained via simulations and has been compared to partial parallel interference cancellation (PPIC) method. A good improvement in performance in the low SNR regions, which is difficult to achieve by conventional multiuser detectors and also important as the actual systems are likely to operate in these regions, has been achieved. All the techniques and their modifications introduced in this work consider the complexity as an important issue that enables them suitable for industry and implementation purposes. Another important feature is that the techniques perform on canonical matrix formulations of the system so they can be applied to MC-CDMA and MIMO systems, as well.
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Suboptimum search algorithm in conjunction with polynomial expanded multiuser detection for uplink
Fifth IEE International Conference on 3G Mobile Communication Technologies, 2004Co-Authors: M. Mozaffaripour, R. TafazolliAbstract:A Suboptimum search algorithm to suppress the interference level in conjunction with the primary stage of the polynomial expanded (PE) linear multiuser detector for the mobile uplink is proposed. The initial stage is improved through mathematical analysis via Rayleigh-Ritz and Gershgorin algorithms in the linear algebra and based on them PER and PEG detectors are introduced. Its performance is also compared with other recently reported methods in the literature, amongst which is a comprehensive method that optimises the weights of the Taylor series asymptotically. The complexity of the initial stage is also evaluated and compared to the recently reported low-complex Fourier interference cancellation method. Depending on the value of the spreading factor of the active users in system, PEG outperforms the Fourier algorithm (in terms of complexity) with a large gap. The technique was compared with Suboptimum techniques that result in best performance and also compared in a DS-CDMA with less complex techniques such as the Fourier interference cancellation method. The Fourier algorithm is also investigated and some comments on its applicability in the FDD DS-CDMA are also made. The structure of the PE method and the Suboptimum search algorithm are well suited together and that makes them collaboratively work without encountering a high level of complexity. Considering the power profile of the users in the Suboptimum search algorithm leads to even less complexity, yet keeps the performance almost the same. The performance of the structure is obtained by simulations and has been compared to the partial parallel interference cancellation (PPIC) method. A good improvement in performance in the low SNR regions, which is difficult to achieve by conventional multiuser detectors and is also important as the actual systems are likely to operate in these regions, has been achieved. All the techniques and their modifications introduced in this work consider the complexity as an important issue that make them suitable for industry and implementation purposes. Another important feature is that the techniques perform on canonical matrix formulations of the system so they can be applied to MC-CDMA and MIMO systems, as well.
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Suboptimum search algorithm in conjunction with iterative linear multiuser detector for uplink
Personal Indoor and Mobile Radio Communications, 2003Co-Authors: M. Mozaffaripour, R. TafazolliAbstract:A Suboptimum search algorithm to suppress the interference level in conjunction with a primary stage of iterative linear multiuser detector for the mobile uplink is proposed. The initial stage is improved through analytical analysis. The structure of the iterative method and the Suboptimum search algorithm are well suited together and makes them collaboratively work without encountering a high level of complexity. Considering the power profile of the users in the Suboptimum search algorithm leaded to even less complexity, yet keeping the performance almost the same. The performance of the structure is obtained by simulations and has been compared to parallel interference cancellation method.
Jacques Verly - One of the best experts on this subject based on the ideXlab platform.
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Design and representation of Suboptimum methods for radar space-time adaptive processing (STAP) techniques using a canonical framework
European Radar Conference 2005. EURAD 2005., 2024Co-Authors: S. De Greve, Fabian D. Lapierre, Jacques VerlyAbstract:Space-time adaptive processing (STAP) is a technique used by moving radars to detect slow moving targets. The goal is to reject interference and noise. However, rejection requires a great number of training samples and a large computational cost. To keep the task manageable, Suboptimum STAP methods (SOMs) have been proposed by several authors. We have developed a framework to encompass all these methods in a canonical structure. In the appendices, some famous SOMs will be described using the canonical framework. The canonical framework can also be seen as a tool that can be used to design new techniques. This paper is a guideline for designing Suboptimum STAP techniques using the framework. Choices that designers have to make are presented in regard with the impact of these choices
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Canonical framework for describing Suboptimum radar space-time adaptive processing (STAP) techniques
Proceedings of the 2004 IEEE Radar Conference (IEEE Cat. No.04CH37509), 2024Co-Authors: S. De Greve, Fabian D. Lapierre, Jacques VerlyAbstract:We address the problem of detecting slow moving targets from a moving radar system using space-time adaptive processing (STAP) techniques. Optimum interference rejection is known to require the estimation and the subsequent inversion of an interference-plus-noise covariance matrix. To reduce the number of training samples involved in the estimation and the computational cost inherent to the inversion, many Suboptimum STAP techniques have been proposed. Earlier attempts at unifying these techniques had a limited scope. In this paper, we propose a new canonical framework that unifies all of the STAP methods we are aware of. This framework can also be generalized to include the estimation of the covariance matrix and the compensation of the range dependence; it applies to monostatic and bistatic configurations. We also propose a new decomposition of the CSNR performance metric that can be used to understand the performance degradation specifically due to the use of a Suboptimum method.
Gan Zheng - One of the best experts on this subject based on the ideXlab platform.
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throughput analysis and optimization of wireless powered multiple antenna full duplex relay systems
IEEE Transactions on Communications, 2016Co-Authors: Mohammadali Mohammadi, Caijun Zhong, Himal A. Suraweera, Batu K. Chalise, Gan Zheng, Ioannis KrikidisAbstract:We consider a full-duplex (FD) decode-and-forward system in which the time-switching protocol is employed by the multiantenna relay to receive energy from the source and transmit information to the destination. The instantaneous throughput is maximized by optimizing receive and transmit beamformers at the relay and the time-split parameter. We study both optimum and Suboptimum schemes. The reformulated problem in the optimum scheme achieves closed-form solutions in terms of transmit beamformer for some scenarios. In other scenarios, the optimization problem is formulated as a semidefinite relaxation problem and a rank-one optimum solution is always guaranteed. In the Suboptimum schemes, the beamformers are obtained using maximum ratio combining, zero-forcing, and maximum ratio transmission. When beamformers have closed-form solutions, the achievable instantaneous and delay-constrained throughput are analytically characterized. Our results reveal that beamforming increases both the energy harvesting and loop interference suppression capabilities at the FD relay. Moreover, simulation results demonstrate that the choice of the linear processing scheme as well as the time-split plays a critical role in determining the FD gains.
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Throughput maximization for full-duplex energy harvesting MIMO communications
2016Co-Authors: Batu K. Chalise, Gan ZhengAbstract:© 2016 IEEE.This paper proposes methods for optimizing bidirectional information rates between a base station (BS) and a wirelessly powered mobile station (MS). In the first phase, the MS harvests energy using signals transmitted by the BS, whereas in the second phase both the BS and MS communicate to each other in a full-duplex mode. The BS-beamformer and the time-splitting parameter (TSP) of energy harvesting scheme are jointly optimized to obtain the BS-MS rate region. The joint optimization is non-convex, however a computationally efficient optimum technique based upon semidefinite relaxation and line-search is proposed to solve the problem. Moreover, a Suboptimum approach based upon the zero-forcing (ZF) beamformer constraint is also proposed. In this case, a closed-form solution of TSP is obtained. Simulation results demonstrate the advantage of the optimum method over the Suboptimum method, especially for smaller values of BS transmit power and number of transmit antennas at the BS
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Throughput analysis and optimization of wireless-powered multiple antenna full-duplex relay systems
2016Co-Authors: Mohammadali Mohammadi, Caijun Zhong, Himal A. Suraweera, Batu K. Chalise, Gan Zheng, Ioannis KrikidisAbstract:© 2016 IEEE.We consider a full-duplex (FD) decode-and-forward system in which the time-switching protocol is employed by the multiantenna relay to receive energy from the source and transmit information to the destination. The instantaneous throughput is maximized by optimizing receive and transmit beamformers at the relay and the time-split parameter. We study both optimum and Suboptimum schemes. The reformulated problem in the optimum scheme achieves closed-form solutions in terms of transmit beamformer for some scenarios. In other scenarios, the optimization problem is formulated as a semidefinite relaxation problem and a rank-one optimum solution is always guaranteed. In the Suboptimum schemes, the beamformers are obtained using maximum ratio combining, zero-forcing, and maximum ratio transmission. When beamformers have closed-form solutions, the achievable instantaneous and delay-constrained throughput are analytically characterized. Our results reveal that beamforming increases both the energy harvesting and loop interference suppression capabilities at the FD relay.Moreover, simulation results demonstrate that the choice of the linear processing scheme as well as the time-split plays a critical role in determining the FD gains
