共查询到20条相似文献，搜索用时 109 毫秒
1.
The distributed event-triggered secure consensus control is discussed for multi-agent systems (MASs) subject to DoS attacks and controller gain variation. In order to reduce unnecessary network traffic in communication channel, a resilient distributed event-triggered scheme is adopted at each agent to decide whether the sampled signal should be transmitted or not. The event-triggered scheme in this paper can be applicable to MASs under denial-of-service (DoS) attacks. We assume the information of DoS attacks, such as the attack period and the consecutive attack duration, can be detected. Under the introduced communication scheme and the occurrence of DoS attacks, a new sufficient condition is achieved which can guarantee the security consensus performance of the established system model. Moreover, the explicit expressions of the triggering matrices and the controller gain are presented. Finally, simulation results are provided to verify the effectiveness of the obtained theoretical results. 相似文献
2.
Approximate mathematical form expressions were derived for the estimation of the average (ergodic) capacity and the average bit error rate of a log-normal free space optical channel in the cases of weak to moderate atmospheric turbulence conditions. We investigate the average capacity, the average bit error rate and the outage probability of free space optical communication channels using the frequentist and the Bayesian approach. Emphasis is given on the cases of weak to moderate atmospheric turbulence leading to channels modeled by log-normal distributed intensity fading. Furthermore, accurate approximate closed-form expressions and estimation procedures for their achievable capacity as well as their bit error rate and the important parameters of interest are derived. The derived approximate analytical expressions are verified by various numerical examples and simulations. Moreover, each methodology is reviewed in terms of their analytic convenience and their accuracy is also discussed. 相似文献
3.
This paper considers the problem of the leader-following consensus of generally nonlinear discrete-time multi-agent systems with limited communication channel capacity over directed fixed communication networks. The leader agent and all follower agents are with multi-dimensional nonlinear dynamics. We propose a novel kind of consensus algorithm for each follower agent based on dynamic encoding and decoding algorithms and conduct a rigorous analysis for consensus convergence. It is proved that under the consensus algorithm designed, the leader-following consensus is achievable and the quantizers equipped for the multi-agent systems can never be saturated. Furthermore, we give the explicit forms of the data transmission rate for the connected communication channel. By properly designing the system parameters according to restriction conditions, we can ensure the consensus and communication efficiency with merely one bit information exchanging between each pair of adjacent agents per step. Finally, simulation example is presented to verify the validity of results obtained. 相似文献
4.
In this paper, the event-triggered non-fragile H∞ fault detection filter is designed for a class of discrete-time nonlinear systems subject to time-varying delays and channel fadings. The Lth Rice fading model is utilized to reflect the actual received measurement signals, and its channel coefficients own arbitrary probability density functions on interval [0,1]. The event-based filter is constructed to reduce unnecessary data transmissions in the communication channel, which only updates the measurement signal to the filter when the prespecified “event” is triggered. Multiplicative gain variations are utilized to describe the phenomenon of parameter variations in actual implementation of the filter. Based on Lyapunov stability theory, stochastic analysis technology along with linear matrix inequalities (LMIs) skills, sufficient conditions for the existence of the non-fragile fault detection filter are obtained which make the filtering error system stochastically stable and satisfy the H∞ constraint. The gains of the filter can be calculated out by solving the feasible solution to a certain LMI. A simulation example is given to show the effectiveness of the proposed method. 相似文献
5.
《Journal of The Franklin Institute》2019,356(12):6741-6756
This paper presents general, closed-form, and exact expressions for cumulative distribution function, probability density function and average value for the ratio of independent η-μ random variables, with arbitrary parameters. More specifically, the outage capacity with peak interference power constraint, the delay-limited capacity, and the ergodic capacity considering constraints on the interference power are derived for non-homogeneous environments containing multipath waves clusters. Numerical curves are presented to evaluate the effects of the general fading variables in spectrum sharing systems. Besides, the results are validated by performing Monte-Carlo simulations. Notably, the provided results find important applications in cognitive radio systems considering the spectrum sharing approach and channels modeled by η-μ distribution. 相似文献
6.
Joy Iong-Zong Chen 《Journal of The Franklin Institute》2007,344(6):889-911
The average level crossing rate (LCR) and average fading duration (AFD) criterions are applied to analyze the selection combining (SC) diversity for wireless communication systems over correlated-Rayleigh and correlated-Rice fading in this paper. The scenarios of the fading channel models are characterized as 4 generalized and experimental distributions, e.g., Rayleigh, Rice, Nakagami-m, and Weibull distributed statistics. Moreover, both of independent and correlated proprieties between branches are also involved for consideration. For purpose of unifying and clarifying the average LCR and AFD performance formulas results from the evaluation for SC diversity, it is not only the results from our research presented, but some of the published results are also cited and illustrated by numerical evaluation again in this study. 相似文献
7.
8.
This paper investigates the optimal tracking performance of the multiple-input multiple-output (MIMO) discrete-time networked control systems (NCSs) considering the quantization of communication channel. The tracking performance is adopted for the H2 square error criterion. The optimal tracking performance expression is obtained by using the co-prime factorization, the partial factorization, the inner–outer factorization and the spectral decomposition methods. Moreover, the paper also includes the exploration of the optimal tracking performance with input power constraint. The obtained results have demonstrated that the optimal tracking performance is influenced by the non-minimum phase zeros, unstable poles and their directions, the reference signal and the quantization interval. Moreover the theoretical results have also been proven using a number of different examples. 相似文献
9.
Multi-sensor data fusion over one channel is studied in this paper. The communication constraint considered here is medium access constraint. When the synchronous time division multiplexing (STDM) mechanism is used to address this problem, collective delay emerges. Collective delay time depends upon the channel capacity and traffic flow assigned to the communication channel, causing contradiction between traffic flow and delay time (the number of transmitted sensors and delay steps). A new model is developed that can truly reflect this contradiction by introducing a stochastic process θ. Based on the obtained system model, the optimal data fusion filter is designed. It also gives the upper bounds of the expected estimation error covariance and estimation error covariance with one-step delay. Two illustrative examples are given in the last section to show the influence of θ on estimation performance. 相似文献
10.
In this paper, the state estimation problem for discrete-time networked systems with communication constraints and random packet dropouts is considered. The communication constraint is that, at each sampling instant, there is at most one of the various transmission nodes in the networked systems is allowed to access a shared communication channel, and then the received data are transmitted to a remote estimator to perform the estimation task. The channel accessing process of those transmission nodes is determined by a finite-state discrete-time Markov chain, and random packet dropouts in remote data transmission are modeled by a Bernoulli distributed white sequence. Using Bayes’ rule and some results developed in this study, two state estimation algorithms are proposed in the sense of minimum mean-square error. The first algorithm is optimal, which can exactly compute the minimum mean-square error estimate of system state. The second algorithm is a suboptimal algorithm obtained under a lot of Gaussian hypotheses. The proposed suboptimal algorithm is recursive and has time-independent complexity. Computer simulations are carried out to illustrate the performance of the proposed algorithms. 相似文献
11.
The performance of a Wideband Code Division Multiple Access (W-CDMA) system using Pseudo Noise (PN) codes and chaotic codes in the presence of a Weibull fading channel is studied in this paper. The W-CDMA system modeled using Gaussian Approximation is analyzed on a Weibull fading channel which fades the amplitude of the transmitted signal randomly according to the Weibull distribution. Closed-form expressions for Bit Error Rate (BER) are derived and expressed in terms of Meijer?s-G function. Performance measures in terms of BER are plotted versus Signal-to-Noise Ratio (SNR) for various values of fading severity, average fading power, and channel memory using PN and chaotic codes. Performance comparison between PN codes and chaotic codes are also analyzed. 相似文献
12.
Zvezdan M. Marjanović Goran T. Djordjević Gradimir V. Milovanović 《Journal of The Franklin Institute》2018,355(2):965-980
In this paper, we analyze detection of multilevel phase-shift keying (MPSK) signals transmitted over a Gamma shadowed Nakagami-m fading channel. We derive novel analytical expression, in terms of Meijer’s G function, for Fourier coefficients of the probability density function of the received signal composite phase. Under the assumption of the imperfect reference signal extraction in the receiver, which is performed from the pilot signal, the analytical expression is derived for the symbol error probability (SEP) in the form of convergent series. The existence of the error floor is identified, and expression for its computation is provided. Mathematical proofs for convergence of Fourier series are provided for both SEP and SEP floor, and novel expressions of upper bounds for truncation errors are derived in terms of elementary mathematical functions. The convergence rate of the derived expressions is examined. Numerical results are confirmed independently by Monte-Carlo simulations. 相似文献
13.
《Information processing & management》2020,57(2):102162
Conversation is the natural mode for information exchange in daily life, a spoken conversational interaction for search input and output is a logical format for information seeking. However, the conceptualisation of user–system interactions or information exchange in spoken conversational search (SCS) has not been explored. The first step in conceptualising SCS is to understand the conversational moves used in an audio-only communication channel for search. This paper explores conversational actions for the task of search. We define a qualitative methodology for creating conversational datasets, propose analysis protocols, and develop the SCSdata. Furthermore, we use the SCSdata to create the first annotation schema for SCS: the SCoSAS, enabling us to investigate interactivity in SCS. We further establish that SCS needs to incorporate interactivity and pro-activity to overcome the complexity that the information seeking process in an audio-only channel poses. In summary, this exploratory study unpacks the breadth of SCS. Our results highlight the need for integrating discourse in future SCS models and contributes the advancement in the formalisation of SCS models and the design of SCS systems. 相似文献
14.
P. Varzakas 《Journal of The Franklin Institute》2006,343(3):295-300
The spectral efficiency of a multi-carrier direct-sequence code-division multiple-access (MC/DS-CDMA) system operating in a Rayleigh fading environment is investigated and evaluated in terms of the theoretically achievable channel capacity (in the Shannon sense) per user, estimated in an average sense. This short paper covers operation of the considered system over broadcast communication randomly time-varying channels as applicable to wireless radio networks and single-cell indoor mobile systems and leads to the derivation of a closed-form expression for the achieved spectral efficiency. Furthermore, the relation between the number of the employed sub-carriers and the achieved spectral efficiency is revealed. 相似文献
15.
Zhou He 《The Information Society》2013,29(3):182-190
As communism loses its tenets as a genuinely believed ideology and becomes a ritualized facet of a regime that strives to prolong and justify its politically and morally shaky mandate, there have emerged two distinct discourse universes in China: the official one and the nonofficial one. Taking advantage of new communication technologies, the nonofficial discourse universe extends its boundaries to such platforms as the Internet and SMS (Short Message Service) messages. This paper examines SMS as a major carrier of the deviant discourse in the following aspects: the development of cell phones from an interpersonal communication technology to a quasi-mass communication channel; the spread of deviant expressions through it; the making of the deviant discourse through SMS; the government's control over SMS; and the role of SMS in increasingly pluralistic political undercurrents in various discourse universes in China. 相似文献
16.
多入多出(MIMO)系统在发射端和接收端分别设置多副天线,采用MIMO技术可以提高信道容量和信道可靠性,降低误码率。正交频分复用(OFDM)是一种特殊的多载波传输方案,各子载波在整个符号周期上正交,各子载波信号子频谱可以互相重叠,提高了频带利用率。MIMO-OFDM技术是OFDM与MIMO技术结合形成的一种新技术,该技术是在OFDM传输系统中采用阵列天线实现空间分集,提高了信号质量。本文中全面介绍了MIMO技术和OFDM技术及两者的结合,分析了实现MIMO-OFDM技术的框架,未来的工作是如何用硬件来仿真实现这个系统。 相似文献
17.
In this paper, the stability of networked control systems (NCSs) with communication constraints at both channels is investigated. A Conventional Round-Robin Scheduling (CRRS) is applied to deal with the communication constraints issue for its simple structure. Furthermore, a Dynamic Round-Robin Scheduling (DRRS), which can preserve the controllability and the detectability of the systems, is considered. For the unreliable communication channels, two independent homogeneous Markov chains are selected to model the packet dropouts phenomenon in the sensor-to-controller (S/C) channel and the controller-to-actuator (C/A) channel. According to the periodic property of the Round-Robin Scheduling (RRS), an auxiliary system with augmented Markov chain is established by the lifting technique to facilitate the stability analysis of the closed-loop system. A necessary and sufficient condition of the exponential mean-square stability for the NCSs is derived. Two illustrative examples are shown to demonstrate the effectiveness of the proposed stability analysis method. 相似文献
18.
The beamforming-based spatial precoding (BBSP) method has been proposed to reduce the overheads of the downlink training and the channel state information feedback in the frequency-division duplex (FDD) massive multiple-input-multiple-output (MIMO) wireless communication systems. However, the original BBSP method suffers from the interference problem at user equipments (UEs) because of using a set of pre-defined fixed beamforming coefficients. Moreover, the BBSP method can not deal with the performance degradation due to mutual coupling (MC) effect because of massive antennas deployed at transmitter and receiver. This paper presents a precoding method that incorporates a beamforming-selection spatial precoding (BSSP) scheme with a population-based stochastic optimization algorithm such that the designed beamforming coefficients can greatly reduce the severe interference between UEs and alleviate the MC effect on the performance of massive MIMO systems. The proposed method can not only achieve better bit error rate (BER) performance than the conventional BBSP method, but also preserves the advantages of the BBSP method having lower overheads of the downlink training and the CSI feedback. In particular, we propose an appropriate fitness function based on an averaged BER formula for the population-based stochastic optimization algorithm to find the optimal beamforming coefficients. Numerical simulations are also presented for both the urban-macro and the urban-micro wireless MIMO scenarios to validate the superior BER performance of the proposed precoding method as compared to the existing BBSP method. 相似文献
19.
《Journal of The Franklin Institute》2019,356(17):10296-10314
This paper investigates the problem of distributed event-triggered sliding mode control (SMC) for switched systems with limited communication capacity. Moreover, the system output and switching signals are both considered to be sampled by distributed digital sensors, which may cause control delay and asynchronous switching. First of all, a novel distributed event-triggering scheme for switched systems is proposed to reduce bandwidth requirements. Then, a state observer is designed to estimate the system state via sampled system output with transmission delay. Based on the observed system state, a switched SMC law and corresponding switching law are designed to guarantee the exponential stability of the closed-loop system with H∞ performance. Finally, an application example is given to illustrate the effectiveness of the proposed method. 相似文献
20.
Shen Yan Mouquan Shen Guangming Zhang Sing Kiong Nguang 《Journal of The Franklin Institute》2019,356(1):58-79
This paper is concerned with the reliable event-triggered H∞ output control of nonlinear systems with actuator faults. A dynamic triggering scheme depending on system outputs is implemented to reduce the amount of communication transmissions, which is different from existing constant triggering thresholds. The parameters of actuator faults are estimated via observer state. To compensate for the fault effects on systems, the reliable controller parameters are adjusted along with the obtained estimations. By using some technical lemmas, new sufficient conditions for the closed-loop system to be asymptotically stable with prescribed H∞ performance are formed in linear matrix inequalities. Lastly, simulations are implemented to demonstrate the validity of the proposed method. 相似文献