State estimation via limited capacity noisy communication channels

The paper addresses a state estimation problem involving communication errors and capacity constraints. Discrete-time partially observed linear systems perturbed by stochastic unbounded additive disturbances are studied. Unlike the classic theory, the sensor signals are communicated to the estimator over a limited capacity noisy digital link modeled as a stochastic discrete memoryless channel. It is shown that the capability of the noisy channel to ensure state estimation with a bounded in probability error is identical to its capability to transmit information with as small probability of error as desired. In other words, the classic Shannon capacity of the channel constitutes the boundary of the observability domain. It is shown that whenever the Shannon capacity bound is met, a reliable observation can be ensured by means of a state estimator consuming a bounded (as time progresses) computational complexity and memory per unit time. The corresponding state estimator is constructed explicitly and is based on the classic block coding approach, so that traditional block encoding–decoding procedures can be employed for its implementation. This work was supported by the Australian Research Council and the Russian Foundation for Basic Research grant 06-08-01386.     

State estimation scheme for nonlinear dynamical systems based on the stochastic approximation

An algorithm for the state estimation of multivariable nonlinear dynamic systems with noisy nonlinear observation systems is investigated on the basis of stochastic approximation procedure.Using an extended version of Dvoretzky's theorem, we derive a sufficient condition that estimation error converges to zero, both in the mean square and with probability one for noise-free multivariable dynamical systems. We then show that our estimation procedure makes the estimation error bounded in the mean square norm for noisy dynamical systems. Some numerical examples are presented for the illustration of the approach mentioned above.     

一类混沌系统的量化同步

针对信息受限的条件,研究了一类连续混沌系统的同步问题.通过一个有限容量的信道,将具有混沌形式的驱动系统和基于观测器的响应系统连接.在这种情况下,设计了有效的量化方法使得同步误差关于传输误差是输入状态稳定(ISS),同时保证传输误差是指数衰减的.从而使得混沌同步误差在信道容量有限条件下渐近趋于零.最后通过数值例子说明了本文方法的有效性.     

Try-once-discard scheduling for stochastic networked control systems

In practical networked control systems (NCS), such as smart grids, cooperative robotics, and sensor networks, often multiple control applications share a communication infrastructure, requiring a smart and efficient scheduling mechanism to coordinate the access to the capacity-limited communication medium. In this article we consider the problem of event-based scheduling design for NCSs consisting of multiple control loops over a shared communication medium. We extend the notion of Try-Once-Discard (TOD), which is one of the basic deterministic event-based scheduling protocols for resource constrained NCSs, to the case of multiple stochastic control systems coupled via a shared communication medium subject to capacity limitation and stochastic packet delivery failure. Showing that the overall network-induced error is a homogeneous Markov chain in our stochastic set-up, we first study stability properties of such networked systems under the TOD scheduling scheme employing the concepts of stochastic stability. Then, we derive sufficient stability conditions under the TOD rule assuming that the communication channel is not ideal, i.e. a scheduled data packet for transmission might be lost in the communication channel with a non-zero probability. Furthermore, we derive analytic performance bounds by finding uniform upper-bounds for an average quadratic cost function. The numerical simulations are performed for variety of system parameters and NCS set-ups to strengthen our stability claim as well as illustrating performance bounds. Additionally, we show that the TOD scheduling rule outperforms the conventional time-triggered, and uniform and non-uniform random channel access arbitration mechanisms, in terms of efficient coordination of channel access in stochastic NCSs.     

On the zero-rate error exponent for a BSC with noisy feedback

For information transmission, a binary symmetric channel is used. There is also another noisy binary symmetric channel (feedback channel), and the transmitter observes (without delay) all outputs of the forward channel via the feedback channel. Transmission of non-exponentially many messages is considered (i.e., the transmission rate is zero). The achievable decoding error exponent for this combination of channels is investigated. It is shown that if the crossover probability of the feedback channel is less than a certain positive value, then the achievable error exponent is better than the similar error exponent of the no-feedback channel. The described transmission method and the corresponding lower bound for the error exponent can be improved, as well as extended to positive transmission rates.     

Internal stability of dynamic quantised control for stochastic linear plants

Existing analyses of ‘zooming’ quantisation schemes for bit-rate-limited control systems rely on the encoder and controller being initialised with identical internal states. Due to the quantiser discontinuity and the plant instability, it was not clear if closed-loop stability was possible if the encoder and controller commenced from different initial conditions. In this article, we consider partially observed, unstable linear time-invariant plants, with unbounded and possibly non-Gaussian noise, and propose a modified zooming-like scheme with finite-dimensional internal encoder and controller states that may not initially be identical. Using a stochastic pseudo-norm, we prove that this scheme yields mean-square stability in all closed-loop state variables, not just the plant state, under a sufficient condition involving this initial error, the plant dynamics and the channel data rate. With diminishing initial error, this condition approaches a known universal lower bound on data rates and becomes tight. Furthermore, we show that the scheme automatically corrects itself, in the sense that the errors between the internal states of the encoder and controller tend to zero stochastically with time. This suggests that the policy will maintain stability in the presence of channel errors, for sufficiently low bit error rates. We support these conclusions with simulations.     

一类离散混沌系统的传输受限同步问题

研究了一类离散混沌系统信息受限条件下的同步问题.将具有离散形式的混沌驱动系统和具有控制输入的响应系统通过一个有限容量信道的通讯网络进行连接.在这种情况下,设计了合适的编解码方法使得传输误差在一定的条件下达到渐近稳定.同时,在线性矩阵不等式条件下,获得了同步误差方程关于传输误差是输入状态稳定,从而实现了混沌系统在信道容量有限条件下的完全同步.最后,通过Fold混沌系统验证了本文方法的有效性.     

Risk-sensitivity conditions for stochastic uncertain model validation

The paper presents sufficient and necessary conditions that verify the relevance of an assumed linear stochastic system model for problems in which probabilistic characteristics of the plant are not known exactly. The approach is to establish the existence of an admissible probability space on which the output of the candidate stochastic system model is consistent (in a stochastic sense) with the noisy output of the plant.     

车联网中车-车通信系统在n-Rayleigh信道下的性能分析

文章在n-Rayleigh衰落信道下,研究了使用选择合并（electioncombining,SC）接收的车—车通信系统的平均符号误码率（average symbol error probability,ASEP）和信道容量性能。文章基于积分法,分别推导了车—车通信系统采用M进制相移键控（M-ary phase shift keying,MPSK）和M进制脉冲幅度调制（M-ary pulse amplitude modulation,MPAM）的平均符号误码率的精确表达式和信道容量的精确表达式。然后在不同系统条件下,分别对平均符号误码率和信道容量性能做了数值仿真,理论分析结果与仿真结果相吻合,验证了理论分析结果的正确性。仿真结果表明,随着分集支路数的增加,系统的ASEP和信道容量性能得到了很好的改善,当使用QPSK调制信噪比为16dB时,分集支路数L=1,系统的误码率是7×10-2,信道容量是4bps/Hz;分集支路数L=2,系统的误码率是1×10-2,信道容量是5.1bps/Hz;分集支路数L=3,系统的误码率是2×10-3,信道容量是5.8bps/Hz。     

Optimal tracking performance of MIMO control systems with communication constraints and a code scheme

This paper investigates the issue of the optimal tracking performance for multiple-input multiple-output linear time-invariant continuous-time systems with power constrained. An H₂ criterion of the error signal and the signal of the input channel are used as a measure for the tracking performance. A code scheme is introduced as a means of integrating controller and channel design to obtain the optimal tracking performance. It is shown that the optimal tracking performance index consists of two parts, one depends on the non-minimum phase zeros and zero direction of the given plant, as well as the reference input signal, while the other depends on the unstable poles and pole direction of the given plant, as well as on the bandwidth and additive white noise of a communication channel. It is also shown that when the communication does not exist, the optimal tracking performance reduces to the existing normal tracking performance of the control system. The results show how the optimal tracking performance is limited by the bandwidth and additive white noise of the communication channel. A typical example is given to illustrate the theoretical results.     

基于合作博弈的认知卫星网络信道分配与上行功率控制算法

随着通信业务需求的不断增长,频谱资源的有限性使得卫星通信网络和地面网络都面临着严重的频谱危机。认知无线电技术的出现,使得卫星网络与地面网络共用频率资源以提升网络效用成为可能。文中对认知接入分配给地面网络作为主用户的同一频谱资源的认知卫星网络的功率控制和信道分配问题进行了研究。根据卫星网络和地面网络的特性构建了合理的系统模型,并利用中断概率门限表征了信道估计误差对系统容量的影响。为了保护主基站的通信性能,在考虑信道估计误差、信道资源约束、认知卫星用户最大发射功率和微波基站干扰约束的条件下,根据议价博弈理论设计了优化函数。其次,根据凸优化理论推导了最优发射功率和信道分配的闭式解,并在此基础上设计了一种对偶迭代算法来求解该优化问题。最后,根据卫星网络的特性设置了合理的网络参数,并根据参数利用Matlab仿真平台对提出的算法进行了仿真实验。仿真结果表明:所提方法在不同到达速率的条件下均具备良好的收敛性;信道估计误差会降低网络的总容量;所提方法在波束数多于15个时,相比比例公平性算法容量提升超过50 bps/Hz,相比最大容量法公平性能提升超过一倍,因此,相较于这两种方法,该方法能在系统容量和用户间公平性之间获得较好的折中。     

基于神经网络的高阶随机非线性系统的状态反馈控制

基于神经网络(NN)研究了一类含有未知非线性项的高阶随机不确定系统的自适应状态反馈控制问题. 通过引入径向基函数神经网络(RBF NN) 逼近方法, 运用 backstepping 技术以及选择合适的 Lyapunov 函数, 我们构造了一个自适应状态反馈控制器使得闭环系统是半全局一致最终有界的. 仿真例子验证了设计方法的有效性.     

Best Tracking Performance of Networked Control Systems Based on Communication Constraints

The best tracking problem for a single‐input‐single‐output (SISO) networked control system with communication constraints is studied in this paper. The tracking performance is measured by the energy of the error signal between the output of the plant and the reference signal. The communication constraints under consideration are finite bandwidth and networked induced‐delay. Explicit expressions of the minimal tracking error have been obtained for networked control systems with or without communication constraints. It is shown that the best tracking performance dependents on the nonminimum phase zeros, and unstable poles of the given plant, as well as the bandwidth and networked induced‐delay. It is also shown that, if the constraints of the communication channel do not exist, the best tracking performance reduces to the existing tracking performance of the control system without communication constraints. The result shows how the bandwidth and networked induced‐delay of a communication channel may fundamentally constrain a control system's tracking capability. Some typical examples are given to illustrate the theoretical results.     

Adaptive chaos synchronization in Chua's systems with noisy parameters

Using the Lyapunov stability theory an adaptive control is proposed for chaos synchronization between two Chua systems which have stochastically time varying unknown coefficients. The stochastic variations of the coefficients around their unknown mean values are modeled through Gaussian white noise produced by the Wiener process. It is shown that using the proposed adaptive control the mean square of synchronization error converges to an arbitrarily small bound around zero depending on the controller feedback gain. Simulation results indicate that the proposed adaptive controller has a high performance in synchronization of chaotic Chua circuits in noisy environment.     

Strong Converse for the Feedback-Assisted Classical Capacity of Entanglement-Breaking Channels

Quantum entanglement can be used in a communication scheme to establish a correlation between successive channel inputs that is impossible by classical means. It is known that the classical capacity of quantum channels can be enhanced by such entangled encoding schemes, but this is not always the case. In this paper, we prove that a strong converse theorem holds for the classical capacity of an entanglement-breaking channel even when it is assisted by a classical feedback link from the receiver to the transmitter. In doing so, we identify a bound on the strong converse exponent, which determines the exponentially decaying rate at which the success probability tends to zero, for a sequence of codes with communication rate exceeding capacity. Proving a strong converse, along with an achievability theorem, shows that the classical capacity is a sharp boundary between reliable and unreliable communication regimes. One of the main tools in our proof is the sandwiched Rényi relative entropy. The same method of proof is used to derive an exponential bound on the success probability when communicating over an arbitrary quantum channel assisted by classical feedback, provided that the transmitter does not use entangled encoding schemes.     

多径和噪声作用下延迟锁定环的测距误差分析

在近距差分ＧＰＳ或者是基于移动通信网的Ｅ９１１用户定们一中,多径干扰都成为主要测距误差源,为分析多径干扰对延迟锁定跟踪误差的影响,本文运用Ｆokker-Planck方程分析了相干伪码跟踪环（ＤＬＬ）,导出了伪距误差概率密度函数解析表达式,给出了Ｍ径条件下的信国距误差均值与方差的简单计算公式,并证明了在一种二阶ＤＬＬ环,它的伪距变化率误差不受多径的影响,恒为零均值正态分布。     

Observer-based tracking controller design for networked predictive control systems with uncertain Markov delays

This paper is concerned with a tracking controller design problem for discrete-time networked predictive control systems. The control law used here is a combined state-feedback control and integral control. Since not all the states are available in practice, a local Luenberger observer is utilised to estimate the state vector. The measured output and estimated state vector are packed together and transmitted to the tracking controller via a communication channel with a limited capacity. Meanwhile, the control signal is also transmitted through a communication network.Network-induced delays on both links are considered for the signal transmission and modelled by Markov chains. Moreover, it is assumed that the elements in Markov transition matrices are subject to uncertainties. In order to fully compensate for network-induced delays, the controller generates a sequence of control signals which are dependent on each possible delay in the feedforward channel. By taking the augmentation twice, we obtain delay-free stochastic closed-loop systems and the controlled output is chosen as the tracking error. Sufficient conditions are provided for the energy-to-peak performance of the closed-loop systems. The feedback gains of the controller can be derived by solving a minimisation problem. Two examples are illustrated to demonstrate the effectiveness of the proposed design method.     

Protocols and minimum capacity for transmission of time-critical message in noisy channel

A time-critical message should be correctly transmitted to the receiver before a specified deadline. If the message is corrupted by transmission noise, it can be retransmitted if the resulting delay does not exceed the specified deadline. If the channel capacity is larger, the transmission time is smaller, the maximum number of retransmissions can be larger and hence the probability χ that the message can be correctly received before the deadline is larger. In this paper, we propose two protocols, called Transmit and Wait Protocol and Continuous Transmission Protocol, for handling transmission and retransmission of time-critical message in noisy channel. To ensure that χ is at least equal to a given requirement χ¹, we determine the minimum capacity required by these two protocols for two noisy channel models: (1) independent error model and (2) bursty (or Markovian) error model. The Transmit and Wait Protocol is very simple but the Continuous Transmission Protocol requires smaller capacity.     

Minimum entropy control of nonlinear ARMA systems over a communication network

In this paper, the entropy concept has been utilized to characterize the uncertainty of the tracking error for nonlinear ARMA stochastic systems over a communication network, where time delays in the communication channels are of random nature. A recursive optimization solution has been developed. In addition, an alternative algorithm is also proposed based on the probability density function of the tracking error, which is estimated by a neural network. Finally, a simulation example is given to illustrate the efficiency and feasibility of the proposed approach.     

基于聚合等级的5G通信下行信道传输控制系统设计

为提高5G通信下行信道的传输稳定性,提升传输控制系统存在的控制效果,设计并开发了基于聚合等级的5G通信下行信道传输控制系统。改装DSP协处理器、通信数据采集器以及信道传输控制器,完成硬件系统的优化。根据信道的空间结构和工作原理,构建通信下行信道模型,判定通信下行信道实时状态。在该模型下,采集通信下行信道的实时传输数据,根据信道的聚合等级,分配信道传输资源。最终从信道增强、发送/接收端、传输干扰、传输速度等方面,实现系统的传输控制功能。通过系统测试实验得出结论,设计系统的传输速率控制误差、信道传输丢包量和信道拥塞概率均有所降低,即设计系统在传输控制功能方面更具优势。