Quantized Feedback Research Articles

Quasi-synchronization of fractional-order complex networks with random coupling via quantized control

We investigate the quasi-synchronization of fractional-order complex networks (FCNs) with random coupling via quantized control. Firstly, based on the logarithmic quantizer theory and the Lyapunov stability theory, a new quantized feedback controller, which can make all nodes of complex networks quasi-synchronization and eliminate the disturbance of random coupling in the system state, is designed under non-delay conditions. Secondly, we extend the theoretical results under non-delay conditions to time-varying delay conditions and design another form of quantization feedback controller to ensure that the network achieves quasi-synchronization. Furthermore, the error bound of quasi-synchronization is obtained. Finally, we verify the accuracy of our results using two numerical simulation examples.

Goodput Maximization With Quantized Feedback in the Finite Blocklength Regime for Quasi-Static Channels

In this paper, we study a quantized feedback scheme to maximize the goodput of a finite blocklength communication scenario over a quasi-static fading channel. It is assumed that the receiver has perfect channel state information (CSI) and sends back the CSI to the transmitter over a resolution-limited error-free feedback channel. With this partial CSI, the transmitter is supposed to select the optimum transmission rate, such that it maximizes the overall goodput of the communication system. This problem has been studied for the asymptotic blocklength regime, however, no solution has so far been presented for finite blocklength. Here, we study this problem in two cases: with and without constraint on reliability. We first formulate the optimization problems and analytically solve them. Iterative algorithms that successfully exploit the system parameters for both cases are presented. It is shown that although the achievable maximum goodput decreases with shorter blocklengths and higher reliability requirements, significant improvement can be achieved even with coarsely quantized feedback schemes.

Event-Triggered Sliding Mode Control of Uncertain Switched Systems via Hybrid Quantized Feedback

This article is concerned with the sliding mode control (SMC) for stabilizing a switched linear system with external disturbances and uncertain nonlinearities. The state sampling is implemented by an event-triggered mechanism (ETM) and the sampled data are transmitted through a limited-bandwidth digital channel. The main challenge of such a work comes from the quantizer saturation and quantization error in the SMC design with finite-level quantization and the mismatched control caused by the switch and event-triggered sampling. To solve the above problem, we at first present an ETM and a limited-information-based SMC law. Then, a new discrete-time level-sets method is proposed to develop the dynamic quantization policy (DQP). If the disturbance bound is known, the DQP can avoid the quantizer saturation without the need of online detection. A switching law and quantization parameter conditions are provided to ensure the convergence of the state trajectory. At last, the result is generalized to the unknown bound of disturbance. The limited-information control problem of a single-link manipulator is taken as a potential application of the proposed method.

Wireless Multimedia Transmission Through Cooperative Spectrum Sharing With Quantized Feedback

A cooperative spectrum-sharing strategy is proposed for a hierarchical multimedia network consisting of a cellular base station transmitting high-priority (HP) data to a user equipment (UE) and multiple device-to-device (D2D) connection pairs which transmit low-priority (LP) signal to offload the cellular data traffic. In implementing the proposed strategy, the precoding design at each D2D transmitter is performed in such a way as to enhance the strength of the HP signal and minimize the interference caused at the UE by the D2D transmission. Furthermore, in accordance with the quantized signal-to-noise ratio (SNR) information reported by the UE for the cellular downlink, each D2D transmitter selects the power allocation factor which maximizes the D2D transmission rate while simultaneously satisfying the outage probability constraint for the HP signal. Having chosen the precoding vectors and power allocation factor for each D2D connection, the D2D transmitter which achieves the maximum D2D transmission rate is selected in a distributed manner via opportunity carrier sensing. The effectiveness of the proposed spectrum-sharing strategy is investigated by means of computer simulations. The results confirm that for most SNR regimes, the proposed strategy successfully meets the outage constraint on the HP signal while simultaneously maximizing the achievable rate of the LP signal.

Stabilization of discrete-time linear systems with quantization and arbitrary packet losses

In this paper, we mainly focus on the stabilization problem of discrete-time linear systems with both quantized input feedback and arbitrary packet losses. The coarsest quantization strategy is analyzed in detail to guarantee the asymptotic stability of the system. If the coarsest quantizer is logarithmic, the necessary and sufficient conditions to asymptotically stabilize such system are converted into some algebraic Riccati equations and then into some LMIs. Then the infimum of the quantization density for the logarithmic quantizer over all packet loss dependent Lyapunov functions is obtained according to these LMIs. In addition, we also prove that the sector bound approach for the logarithmic quantizer is still valid for the system with arbitrary packet losses. The problem of asymptotic stability can be converted into a robust control problem with sector bound uncertainties. The robust stability of the uncertain system is formulated into some LMIs. Finally, an example is given to show the effectiveness of the results obtained in this paper.

A sliding sector approach to quantized feedback variable structure control

This paper is concerned with the quantized feedback quadratic stabilization problem for linear time-invariant systems. Sliding sector based quantized state feedback variable structure control schemes are established. The main benefit of the sliding sector technique is that it can avoid chattering caused by the utilization of variable structure control strategy. With the proposed discrete on-line adjustment of the quantization parameter, it is shown that the proposed sliding sector based sliding mode controllers can tackle state quantization and guarantee quadratic stability of the closed-loop system. Simulation results are given to verify the effectiveness of the proposed method.

Stability Analysis of Discrete-Time Systems With Quantized Feedback and Measurements

This paper considers a quantized system with finite-level quantized input computed from quantized measurements (QIQM). The problem of globally asymptotic stability of QIQM system is transferred to the one of an equivalent system depending on a multiplier which is nonnegative and bounded. It is the focus of this paper to discuss the nonnegativity and boundness of the multiplier. A sufficient condition is given for the globally asymptotic stability of QIQM system. Note the main method used here is similar to the one used by Richter and Misawa, in which the uniform quantizer is employed. This paper is the extension of that work to the logarithmic quantization which is more advantage than the uniform one. A numerical simulation is presented at last to show the effectiveness of the main results and the advantage of logarithmic quantization compared to uniform quantization.

H∞ Control of Fuzzy Impulsive Systems with Quantized Feedback

This paper is concerned with the problem of H∞ control of fuzzy nonlinear impulsive systems with quantized feedback. New results on the H∞ feedback control are established for one class of fuzzy nonlinear uncertain impulsive systems and one class of fuzzy nonlinear impulsive systems with nonlinear uncertainties by choosing appropriately quantized strategies and applying Lyapunov function approach, respectively.

Input-to-State Stability of Differential Inclusions with Applications to Hysteretic and Quantized Feedback Systems

Input-to-state stability (ISS) of a class of differential inclusions is proved. Every system in the class is of Lur'e type: a feedback interconnection of a linear system and a set-valued nonlinearity. Applications of the ISS results, in the context of feedback interconnections with a hysteresis operator or a quantization operator in the feedback path, are developed.

Input-to-State Stabilization of Nonlinear Systems with Quantized Feedback

This paper addresses the stabilization problem of nonlinear feedback systems with quantized measurements in the presence of bounded disturbances. This paper is an extension of [Liberzon, Nešić (2007)] to nonlinear systems. Using the scheme proposed in [Liberzon, Nešić (2007)], we show that input-to-state stability with respect to bounded disturbances is achievable for nonlinear systems with quantized feedback.

A Discrete-Time Control Algorithm Applied to Closed-Loop Pacing of HL-1 Cardiomyocytes

Electrical stimulation represents a useful tool for electrophysiologic investigation of electrically excitable cells such as cardiomyocytes. The stimulation threshold and electrophysiologic response to precisely timed pulses yields valuable information regarding physiologic processes. However, determining these parameters accurately, while simultaneously resolving time-dependent or transient effects has been difficult or impossible with previous methods. This paper presents a discrete-time algorithmic controller used for closed-loop electrical stimulation of HL-1 clonal cardiomyocytes cultured on, and stimulated using, a planar microelectrode array. We introduce the temporal error-controlled algorithm (TECA), that is well-suited to control using capture fraction, a low data rate, highly quantized feedback parameter describing stimulation efficacy. HL-1 cardiomyocytes were electrically stimulated and resulting parameters were used to develop a representative model of partial capture, enabling extensive analysis of the algorithm. The performance of this approach is compared via computer simulation to a previously introduced conditional convergence algorithm to quantify its performance and relative advantages. Operation of the TECA is demonstrated by tracking the real-time biological response of stimulation threshold to a rapid increase in extracellular potassium concentration in four independent cell cultures. This work enables the use of stimulation threshold as a real-time, continuously monitored parameter with considerable utility in cardiac pharmacology, electrophysiology, and cell-based biosensing.

Design and Analysis of MIMO Spatial Multiplexing Systems With Quantized Feedback

This paper investigates the problem of transmit beamforming in multiple-antenna spatial multiplexing (SM) systems employing a finite-rate feedback channel. Assuming a fixed number of spatial channels and equal power allocation, we propose a new criterion for designing the codebook of beamforming matrices that is based on minimizing an approximation to the capacity loss resulting from the limited rate in the feedback channel. Using the criterion, we develop an iterative design algorithm that converges to a locally optimum codebook. Under the independent identically distributed channel and high signal-to-noise ratio (SNR) assumption, the effect on channel capacity of the finite-bit representation of the beamforming matrix is analyzed. Central to this analysis is the complex multivariate beta distribution and tractable approximations to the Voronoi regions associated with the code points. Furthermore, to compensate for the degradation due to the equal power allocation assumption, we propose a multimode SM transmission strategy wherein the number of data streams is determined based on the average SNR. This approach is shown to allow for effective utilization of the feedback bits resulting in a practical and efficient multiple-input multiple-output system design

The application of complex quantized feedback in integrated wireless receivers

Integrated wireless receiver architectures, such as direct-conversion receivers, offer many advantages over the conventional heterodyne receivers including smaller size, lower cost, and reduced power consumption. However, the design of monolithic receivers, using direct-conversion, involves many challenges including dealing with low-frequency disturbances, namely, dc-offset and 1/f noise (especially in CMOS implementations), in-phase (I) and quadrature (Q) amplitude and phase mismatch, local oscillator (LO) leakage, and even-order distortions. A cost-effective method to minimize the low-frequency disturbances is to use ac-coupling in the baseband signal path. However, it results in baseline wander effects, especially in spectrally efficient modulation schemes such as quadrature amplitude modulation (QAM) where the baseband signal spectrum contains a significant amount of energy near dc. A system solution to mitigate the effects of low-frequency disturbance is presented in this paper. The quantized feedback (QFB) technique is used in conjunction with ac-coupling to minimize the baseline wander effects. A cross-coupled (CC) QFB extension to compensate for the receiver local oscillator phase error as well as the IQ mismatch is also described. Simulation results are presented to demonstrate the effectiveness of this complex QFB technique

Quantized Stabilization of Linear Systems: Complexity Versus Performance

Quantized feedback control has been receiving much attention in the control community in the past few years. Quantization is indeed a natural way to take into consideration in the control design the complexity constraints of the controller as well as the communication constraints in the information exchange between the controller and the plant. In this paper, we analyze the stabilization problem for discrete time linear systems with multidimensional state and one-dimensional input using quantized feedbacks with a memory structure, focusing on the tradeoff between complexity and performance. A quantized controller with memory is a dynamical system with a state space, a state updating map and an output map. The quantized controller complexity is modeled by means of three indexes. The first index L coincides with the number of the controller states. The second index is the number M of the possible values that the state updating map of the controller can take at each time. The third index is the number N of the possible values that the output map of the controller can take at each time. The index N corresponds also to the number of the possible control values that the controller can choose at each time. In this paper, the performance index is chosen to be the time T needed to shrink the state of the plant from a starting set to a target set. Finally, the contraction rate C, namely the ratio between the volumes of the starting and target sets, is introduced. We evaluate the relations between these parameters for various quantized stabilizers, with and without memory, and we make some comparisons. Then, we prove a number of results showing the intrinsic limitations of the quantized control. In particular, we show that, in order to obtain a control strategy which yields arbitrarily small values of T/lnC (requirement which can be interpreted as a weak form of the pole assignability property), we need to have that LN/lnC is big enough.