This work describes a novel nonparametric identification method for estimating impulse responses of the general two-inputsingle-output linear system with its target application to the individualization of an empirica...
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This work describes a novel nonparametric identification method for estimating impulse responses of the general two-inputsingle-output linear system with its target application to the individualization of an empirical model of type 1 diabetes. The proposed algorithm is based on correlation functions and the derived generalization of the Wiener-Hopf equation for systems with two inputs, while taking the stochastic properties of the output measurements into account. Ultimately, this approach to solving the deconvolution problem can be seen as an alternative to widely used prediction error methods. To estimate the impulse response coefficients, the generalized least squares method was used in order to reflect nonuniform variances and nonzero covariances of the stochastic estimate of the cross-correlation functions, hence yielding the minimum variance estimator. Estimate regularization strategies were also involved, while three different types of penalties were applied. The combination of smoothing, stability, and causality regularization was proposed to improve the general validity of the estimate and also to lower its variance. The findings of this identification method are meant to be applied within an eventual predictive control synthesis for the artificial pancreas, so a procedure for transforming the nonparametric model into the transfer function-based parametric model was also described. A discussion on the results of a comprehensive simulation-based experiment concludes the paper.
Millimetre wave (mmWave) signal is promising for the challenge of bandwidth shortage and can motivate the research on large-scale antenna arrays. In this paper, the authors investigate the hybrid precoding design that...
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Millimetre wave (mmWave) signal is promising for the challenge of bandwidth shortage and can motivate the research on large-scale antenna arrays. In this paper, the authors investigate the hybrid precoding design that combines with a radio frequency (RF) precoder and a digital precoder for multi-user multiple-inputsingle-output (MU-MISO) systems with large-scale antenna arrays. In practical large-scale antenna array systems, the small antenna spacing and the properties of a scattering environment can create a correlation between channel coefficients for separated receive units. Such correlation prejudices the performance of multi-user systems. This study proposes two approaches to reduce the channel correlation by the hybrid precoding structure. The first approach selects some vectors with the smallest influence with each other from all array response vectors to design an angular-based RF precoder. The second approach optimises the singular values characteristic of the virtual channel matrix before digital processing for the RF precoder. Then, the MU-MISO baseband precoding is implemented by reduced RF chains. Numerical results show that they have different performance depending on the environment. The first can achieve better performance when the channel correlation is not too high, while the second is more effective when the channel realisation is terribly ill-conditioned, especially for higher signal-noise ratio (SNR).
In this study, the effective rate of two-wave with diffused power (TWDP) fading channel is investigated by considering multiple-input single-output systems under delay constraints. The effective rate is particularly f...
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In this study, the effective rate of two-wave with diffused power (TWDP) fading channel is investigated by considering multiple-input single-output systems under delay constraints. The effective rate is particularly focused because it can be used to perform channel-capacity analysis while considering the delay aspect. The classical fading models such as the Rayleigh and Rician models are special cases of a TWDP fading model. In the exact analysis of the effective rate, a new analytical expression is derived for TWDP fading channels. Moreover, the tractable closed-form effective-rate expressions are deduced for high and low signal-to-noise-ratio regimes in the asymptotic analysis. In addition, all these expressions are presented for a single transmitting antenna, i.e. N = 1 (single-inputsingle-output system). The numerical results demonstrate that the effective rate increases by increasing the number of transmitting antennas N and channel-fading parameter K. In contrast, the stringent delay constraints and equal strengths of the specular components cause a reduction in the effective rate.
We consider a multiple-inputsingle-output wireless powered communication network (WPCN), where the single-antenna users harvest energy from a multi-antenna access point (AP) and then transmit information back to the ...
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We consider a multiple-inputsingle-output wireless powered communication network (WPCN), where the single-antenna users harvest energy from a multi-antenna access point (AP) and then transmit information back to the AP. With multiple antennas, the AP can perform energy beamforming in the downlink and exploit multiplexing- or (receive) beamforming-gain in the uplink. We consider maximizing the sum of the users' energy efficiencies (EEs) by jointly optimizing the energy beamforming of the AP, transmit powers of the users, and time allocation. We formulate EE maximization problems for both TDMA-based WPCN (T-WPCN) and SDMA-based WPCN (S-WPCN), which are non-convex because they have the sum-of-ratios objective functions. We optimally solve the former by reformulating it into an equivalent parametric problem, whose solution can be obtained by iteratively solving convex problems, while the latter is optimally solved by convexifying it using the so-called feasible set reduction scheme. We show that the T-WPCN outperforms S-WPCN when there is no minimum throughput requirement, while we can observe that the S-WPCN outperforms T-WPCN when minimum throughput requirement is high. The simulation results verify our theoretical findings and demonstrate the effectiveness of our proposed schemes.
multiple-input single-output systems are employed in free-space optical links to mitigate the degrading effects of atmospheric turbulence. We formulate the power scintillation as a function of transmitter and receiver...
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multiple-input single-output systems are employed in free-space optical links to mitigate the degrading effects of atmospheric turbulence. We formulate the power scintillation as a function of transmitter and receiver coordinates in the presence of weak atmospheric turbulence by using the extended Huygens Fresnel principle. Then the effect of the receiver aperture averaging is quantified. To get consistent results, parameters are chosen within the range of validity of the wave structure functions. Radial array beams and a Gaussian weighting aperture function are used at the transmitter and the receiver, respectively. It is observed that the power scintillation decreases when the source size, the ring radius, the receiver aperture radius, and the number of array beamlet increase. However, increasing the number of array beamlets to more than three seems to have negligible effect on the power scintillation. It is further observed that the aperture averaging effect is stronger when radial array beams are employed instead of a single Gaussian beam. (C) 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)
Time Reversal (TR) has been identified as a promising technique for green communications thanks to its focusing properties and it has been shown that Equal Gain Transmission (EGT) has similar focusing properties. TR a...
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ISBN:
(纸本)9781479973842
Time Reversal (TR) has been identified as a promising technique for green communications thanks to its focusing properties and it has been shown that Equal Gain Transmission (EGT) has similar focusing properties. TR and EGT are perfectly suited to millimeter (mm)-waves band as their performance increases with the transmission bandwidth size and can therefore be applied to IEEE 802.11 amendment ad to perform highly energy-efficient multi-gigabit transmissions. This paper studies TR and EGT application to IEEE 802.11 directional multi-gigabit orthogonal frequency-division multiplexing physical layer (PHY). Efficiency is demonstrated with the help of a channel propagation analysis and bit error rate performance of different line of sight and non-line of sight propagation scenarios and single-inputsingle-output and multiple-inputsingle-output configurations.
Multi-loop integral control is still one of the most popular control strategies in industry due to its simplicity, efficiency, offset free tracking, and capability for fault tolerance. Skogestad and Morari introduced ...
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ISBN:
(纸本)9781922107633
Multi-loop integral control is still one of the most popular control strategies in industry due to its simplicity, efficiency, offset free tracking, and capability for fault tolerance. Skogestad and Morari introduced Decentralized Integral Controllability (DIC) to investigate the decentralized unconditional stability under multi-loop integral control for square systems. However, in engineering practice, some multivariable processes may not be square, which often utilize multiple redundant control inputs for the regulation of only one singleoutput. This study extends the concept of Decentralized Integral Controllability to non-square systems, and presents sufficient conditions for multiple-inputsingle-output nonlinear processes based on singular perturbation analysis. The proposed controllability analysis method is applied in the control of a real time temperature control system and achieves desired temperature tracking results.
In this paper, we propose two novel pre-equalization schemes for multiple-inputsingle-output (MISO) direct-sequence ultra-wideband (DS-UWB) systems with pre-Rake combining and symbol-by-symbol detection. The first sc...
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In this paper, we propose two novel pre-equalization schemes for multiple-inputsingle-output (MISO) direct-sequence ultra-wideband (DS-UWB) systems with pre-Rake combining and symbol-by-symbol detection. The first scheme employs one pre-equalization filter (PEF) per transmit antenna, whereas in the second scheme, the simplified PEF (S-PEF) scheme, all transmit antennas share the same PEF. For both schemes the optimum finite impulse response (FIR) and infinite impulse response (IIR) PEFs are calculated based on the minimum mean Squared error (MMSE) criterion. Our approach is sufficiently general to include also reduced-complexity versions of pre-Rake combining that employ a limited number of Rake fingers. We show that under certain conditions the S-PEF scheme achieves the same performance as the more complex PEF scheme. We also demonstrate that a single-inputmultiple-output (SIMO) DS-UWB system with post-Rake combining and MMSE post-equalization is the dual system to the considered MISO DS-UWB system with pre-Rake combining and MMSE pre-equalization. This uplink-downlink duality can be exploited for efficient calculation of the PEFs and for complexity reduction. Our simulation results show that the proposed PEF schemes achieve significant performance gains over pre-Rake combining without equalization, even if only short PEFs are employed.
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