A DYNAMIC BANDWIDTH CONTROL SCHEME OF VP IN ATM NETWORKS

This paper proposes an efficient adaptive bandwidth allocation scheme of virtual paths. The bandwidth of a virtual path is dynamically adjusted according to the link residual capacity. The scheme can remarkably reduce the load on node processing and simplify the network architecture, while keeping higher transmission efficiency. The excellent performance is proved by detailed theoretical analyses.

Effects of Physical Parameters and Time-Delay Coefficients on the Amplitude and Frequency Bandwidth of Saturation Controller for a Beam Vibration

In this paper, the influence of physical parameters on the width of saturated control frequency band and the influence of time delay parameters on the stability of saturated control system are studied. The analytical solution of the motion equation of the system when the main resonance and the 1:2 internal resonance occur simultaneously is obtained by multiple scale method, experimentally measured natural frequencies of nonlinear beams. The effects of excitation amplitude, delay feedback coefficients and nonlinear coefficients on saturation control are investigated. The results of the study show that the bandwidth of the saturation control can be increased by increasing the value of the external excitation, the nonlinear coefficients enhance the nonlinear phenomena of the system.

A Bandwidth Control Method Providing Entrance QoS for Multimedia Communication

With the development of wideband IP network, many new IP-Based multimedia applications appear ceaselessly. The real-time multimedia application requires that the IP network provides QoS. To the end-to-end real-time multimedia communication, the QoS service includes the trunk QoS and the entrance QoS. The trunk QoS has some feasible technologies, such as RSVP and DiffServ. But, the entrance QoS has few technologies at the moment. So, this paper introduces the entrance bandwidth control to get the end-to-end QoS. The design and scheme of bandwidth controller applying to the usual Internet application and real-time media communication is provided in this paper. It distinguishes between the usual 1nternet applications, such as HTTP and FTP, and the real-time multimedia applications, such as Internet telephony and videoconferencing. Then they will be dealt with in different ways in order to satisfy the QoS requirements of different types of services. In this paper, we propose a new bandwidth control method for real-time multimedia communication. The principle, the implementing flow, the control policy and the application scheme are discussed.

Thermally Controllable Break Junctions with High Bandwidths and High Integrabilities

Break junctions are important in generating nanosensors and single molecular devices. The mechanically con- trollable break junction is the most widely used method for a break junction due to its simplicity and stability. However, the bandwidths of traditional devices are limited to about a few hertz. Moreover, when using traditional methods it is hard to allow independent control of more than one junction. Here we propose on-chip thermally controllable break junctions to overcome these challenges. This is verified by using finite element analysis. Adopting microelectromechanical systems produces features of high bandwidth and independent controllability to this new break junction system. The proposed method will have a wide range of applications on on-chip high speed independent controllable and highly integrated single molecule devices.

带宽化调节下的抗扰PID退饱和控制方法

比例–积分–微分(PID)控制的抗饱和设计是一类经典非线性控制问题,理论研究丰富,但工程中广泛使用的仍是积分退饱和这类简易策略.究其原因,现有理论方法过于依赖系统模型和状态空间理论,稳定性条件与调参机制之间关系复杂.本文基于经典退饱和控制结构,首次阐述了“退饱和带宽”概念及退饱和参数调节机理,在此基础上讨论了两类低阶退饱和补偿器的带宽化设计方法.在抗扰PID反馈控制下,结合小增益定理得到退饱和控制的稳定性条件,给出控制参数与退饱和带宽之间的调节关系,实现退饱和控制的带宽化整定.最后,通过数值仿真验证了所提方法的有效性.

面向2G~5G通信的双频双极化基站天线设计

为满足多种通信制式融合的无线通信需求,提出一款覆盖2G、3G、LTE、Sub-6 GHz波段的交叉偶极子基站天线。2对呈±45°正交的偶极子用以实现天线的双极化特性,辐射单元中的扇形内环、钻石状的外环分别对应天线要实现的低频以及高频波段,可以通过对内环以及外环结构参数的调整实现对2个频段的独立控制。天线上方的寄生贴片用以优化天线阻抗匹配。通过制作实物,测得天线在2个频段分别具有49.9%(1.70~2.80 GHz)和19.2%(3.20~3.88 GHz)的相对带宽,隔离度整体优于20 dB,主视轴的交叉极化比优于21 dB,2个波段的半功率波束宽分别为66°±5°、78°±6°。与已有研究比较,该天线结构简单,在交叉极化和增益方面具有显著优势。

基于改进机器学习的无人机中继通信数据调度控制研究

为解决无人机通信网络中数据调度行为中断概率过大的问题,实现对通信资源的合理分配,提出基于改进机器学习的无人机中继通信数据调度控制方法;设计基本网络架构,联合BMRC协议,设置URLLC数据链路单元,联合相关通信数据样本,求解通信中断概率的具体数值,实现对无人机中继通信网络资源的联合优化处理;分别计算时隙分配参量与带宽分配参量,并以此为基础,确定无人机中继位置,实现对中继通信资源的调度;按照机器学习算法标准,定义PCA改进特征,从而完善改进机器学习算法,再联合最优控制器闭环,实现对通信数据调度行为的控制;实验结果表明,改进机器学习算法作用下,随着中继数据累积量的增大,无人机通信网络中数据调度行为中断概率的最大值只能达到7.3%,有效降低了中断概率,符合合理分配通信资源的实际应用需求。

基于迭代策略的自适应ADRC磁轴承控制仿真

针对磁悬浮轴承位置控制过程中存在非线性耦合、内外部扰动不确定性的问题,提出了一种基于自抗扰控制的四自由度磁轴承迭代学习控制策略。首先依据四自由度磁悬浮轴承系统模型搭建自抗扰控制器,其次将估计的总扰动通过间接迭代控制在线调整扩张状态观测器的带宽,实现不同增益下观测器参数的自适应整定。Simulink仿真实验数据表明:系统约在0.14 s处达到稳定,加入干扰后约0.05 s恢复稳定;基于迭代控制的自适应ADRC四自由度磁悬浮轴承控制性能好,同时调节速度快,具有较强的抗干扰能力。经比例-微分型间接迭代学习控制律在线更新带宽后,超调量小且跟踪目标误差积分性能指标小。

基于带宽优化的ControlNet拥塞避免策略

为了提高ControlNet的快速性和稳定性,提出了基于带宽优化的网络拥塞避免策略。由于ControlNet是由一些相互关联的节点组成的,可以采用生产者/消费者多节点网络的带宽优化方法来控制单个节点的信息传输,提高了网络利用率。根据生产者/消费者多节点网络的通信机制,总结出一套高效的带宽优化算法,并给出详细的算法步骤。以CPU利用率、平均带宽利用率和峰值带宽利用率作为衡量ControlNet网络性能的重要指标,对所设计的带宽优化算法进行验证,实验结果表明,所提出的带宽优化算法能有效解决ControlNet的网络拥塞问题。

ACOUSTICAL TRANSMISSION LINE MODEL FOR ULTRASONIC TRANSDUCERS FOR WIDE-BANDWIDTH APPLICATION

An improved model for ultrasonic transducers is proposed. By considering only the first symmetric mode, each layer is represented as an acoustical transmission line in modeling of bulk wave transducers. In imaging applications, wide bandwidth and short time duration are required. The approach we have used consists of impedance matching the front face of the piezoelectric transducer to the propagating medium with a quarter wavelength impedance matching layer and inserting an nnmatching quarter wavelength acoustical layer between the rear face and backing material. A heavy backing would degrade the wide-band phenomena, but show a time duration shorter than 0.5 μs for imaging applications. PSPICE code of the controlled source model is implemented to precisely predict the performance of the matched transducers such as impedance, insertion loss, bandwidth and duration of the impulse response. Good agreement between the simulation and experimental results has been achieved.

Dynamic resource management using bandwidth brokers

The admission control issue in the design of a centralized bandwidth broker model for dynamic control and management of QoS provisioning is studied. A two-phase differentiated flow treatment based dynamic admission control scheme under the centralized bandwidth broker model is proposed. In the proposed scheme, the flow requests are classified into two classes and get differentiated treatment according to their QoS demands. We demonstrate that this admission control scheme can not only improve the resource utilization but also guarantee the flows＇ QoS. Furthermore, the admission control is divided into two phases： edge admission control and interior admission control. During the interior phase, the PoQ scheme is adopted, which enhances the call processing capability of the bandwidth broker. The simulation results show that the proposed scheme can result in lower flow blocking probability and higher resource utilization. And it also reduces the number of QoS state accesses/updates, thereby increasing the overall call processing capability of the bandwidth broker.

Streaming and congestion control using scalable video coding based on H.264/AVC

This paper presents a streaming system using scalable video coding based on H.264/AVC. The system provides a congestion control algorithm supported by channel bandwidth estimation of the client. It uses retransmission only for packets of the base layer to disburden the congested network. The bandwidth estimation allows for adjusting the transmission rate quickly to the current available bandwidth of the network. Compared to binomial congestion control, the proposed system allows for shorter start-up times and data rate adaptation. The paper describes the components of this streaming system and the results of experiments showing that the proposed approach works effectively for streaming video.

Joint Optimization of Admission Control and Rate Adaptation for Video Sharing over Multirate Wireless Community Cloud

Emerging wireless community cloud enables usergenerated video content to be shared and consumed in a social context. However, the nature of shared wireless medium and timevarying channels seriously limits the quality of service(QoS), partially owing to the lack of mechanisms for effectively utilizing multi-rate channel resources. In this paper, the joint optimization of admission control and rate adaptation is proposed, resulting in a bandwidth-aware rate-adaptive admission control(BRAC) scheme to provide bandwidth guarantee for sharing social multimedia contents. The analytical approach leads to the following major contributions:(1) a bandwidth-aware rate selection(BRS) algorithm to optimally meet the bandwidth requirement of the data session and channel conditions at the physical layer;(2) a routing-coupled rate adaption and admission control algorithm to admit data sessions with bandwidth guarantee. Moreover, extensive numerical simulations suggest that BRAC is efficient and effective in meeting the bandwidth requirements for sharing social multimedia contents. These insights will shed light on communication system implementation for multimedia content sharing over multirate wireless community cloud.

A high-temperature superconducting filter with controllable transmission zero

This paper presents a novel microstrip feedline structure to introduce an extra and controllable transmission zero（TZ）with high rejection for a narrowband filter. This structure loads a reconfigurable capacitor at the end of the input feedline without changing the main structure of the filter. The capacitor is recognized by a 2-bit inter-digital capacitor array. The asymmetrical microstrip feedline structure is suitable for multiple-pole filter designs. A low-loss six-pole high-temperature superconducting bandpass filter with a reconfigurable TZ is designed and fabricated. The center frequency of the filter is 5.22 GHz with TZ at the lower stopband. The TZ can be tuned among four different states. The out-of-band rejection at the TZ frequency is higher than 90 d B, and the insertion loss is lower than 0.92 d B. The measured results are consistent with the simulations.

弱电网条件下并网逆变器控制环路稳定判据及交互作用规律分析

为分析新能源并网发电系统中弱电网与逆变器交互作用对稳定性的影响,该文从控制器带宽交叠角度出发,将表征系统闭环稳定性能的电流环开环传递函数G0表示为电网阻抗、锁相环和电流控制器3个环节相乘,进而把锁相环和电网阻抗环节组合并与电流控制器环节相比得到等效的环路比表达式,据此提出弱电网下基于奈奎斯特定理的并网逆变器控制环路稳定判据,当G0分子和分母幅值相等时,幅频曲线产生交点,易使系统闭环增益无穷大而失稳。接着,为分析3个环节间交互作用规律,该文推导得到满足控制环路稳定判据的锁相环与电流控制器带宽比n的表达式,研究发现:在不同弱电网条件下,带宽比大于n的临界值时,各环节间会产生交互作用,在波德图中主要表现为G0分子和分母幅频曲线的交叠,且电网越弱或锁相环与电流控制器带宽越接近,幅频曲线交叠面积越大,越易导致闭环增益无穷大,即系统愈易失稳;此外,当电流控制器带宽固定时,n的临界值随电网减弱在小于1和大于1之间的区间范围变化,即锁相环与电流控制器的带宽比大于或小于1都可以使得系统保持稳定。最后,通过Matlab仿真和半实物实验平台验证了该文理论分析的准确性。

A switched system approach to stabilization of networked control systems

A switched system approach is proposed to model networked control systems （NCSs） with communication constraints. This enables us to apply the rich theory of switched systems to analyzing such NCSs. Sufficient conditions are presented on the stabilization of NCSs. Stabilizing state/output feedback controllers can be constructed by using the feasible solutions of some linear matrix inequalities （LMIs）. The merit of our proposed approach is that the behavior of the NCSs can be studied by considering switched system without augmenting the system. A simulation example is worked out to illustrate the effectiveness of the proposed approach.

Discrete Quasi-Sliding Mode Tracking Controller with Time Delay Technique

Robust discrete quasi-sliding mode tracking controller is developed with discrete reaching law for trajectory tracking in the presence of modeling uncertainty and unknown disturbance. The conventional prior knowledge of uncertainty upper bounds being replaced by an on-line estimation used in the controller to cancel the slowly varying uncertainties by the mechanism of time delay. This method reduces the feedback gain substantially and improves tracking accuracy. The system behavior in the vicinity of the sliding surface is examined for the existence and bandwidth of quasi-sliding mode. Simulation results show the effectiveness of the strategy.

An adaptive mechanism to guarantee the bandwidth fairness of TCP flows

End-to-end TCP (transmission control protocol) congestion control can cause unfairness among multiple TCP connections with different RTT (Round Trip Time). The throughput of TCP connection is inversely proportional to its RTT. To resolve this problem, researchers have proposed many methods. The existing proposals for RTT-aware conditioner work well when congestion level is low. However, they over-protect long RTT flows and starve short RTT flows when congestion level is high. Due to this reason, an improved method based on adaptive thought is proposed. According to the congestion level of networks, the mechanism can adaptively adjust the degree of the protection to long RTT flows. Extensive simulation experiments showed that the proposed mechanism can guarantee the bandwidth fairness of TCP flows effectively and outperforms the existing methods.

Control Access Point of Devices for Delay Reduction in WBAN Systems with CSMA/CA

Due to the gathering of sickrooms and consultation rooms in almost all hospitals, the performance of wireless devices system is deteriorated by the increase of collision probability and waiting time. In order to improve the performance of wireless devices system, relay is added to control the access point and then the access of devices is distributed. The concentration of access point is avoided and then the performance of system is expected to be improved. The discrete time Markov chain (DTMC) is proposed to calculate the access probability of devices in a duration time slot. The collision probability, throughput, delay, bandwidth and so on are theoretically calculated based on the standard IEEE802.15.6 and the performance of the system with and without relay is compared. The numerical result indicates that the performance of the system with control access point is higher than that of the system without control access point when the number of devices and/or packet arrive rate are high. However, the system with control access point is more complicated. It is the trade-off between the performance and the complication.