基于贪心流量调度的智能变电站过程层网络拓扑高可用无缝冗余配置方法

泛在电力物联网背景下,智能变电站中负责运行状态上传与控制命令下达的过程层网络负载将急剧升高。传统IEC61850标准协议中的高可用性无缝冗余(High-Availability Seamless Redundancy,HSR)通信链路配置方法由于数据副本在存在环路的网络内循环产生额外流量与额外传输延时,存在信息传输实时性差的缺点。因此,提出基于贪心流量优化算法的过程层网络拓扑高冗余无缝配置方法。首先,在分析采用HSR技术的智能变电站过程层网络工作原理的技术上,提出两种高可用性无缝冗余配置方案:交叉(Cross-Links,CLs)方案与四连通环(Four-Connected Rings,FCRs)方案。其次,为避免过程层网络在流量汇聚时易产生拥塞导致传输时效性变差,提出基于贪心算法的流量调度策略。最后,基于Opnet的变电站仿真算例表明,与传统网络拓扑配置方案相比,所提方案的数据平均传输跳数与传统拓扑方案比下降50%,而采用贪心算法的过程层网络流量调度策略在数据拥塞时的传输延时、丢包率和吞吐量衰退服务分别降低32.7%,63.5%和33.3%。因此,所提方案能够显著提升智能变电站过程层网络性能。     

基于PTN配电通信网的QoS研究

针对现有配电通信网业务流传输中的不足,将分组传送网技术引入到配电通信网中,提出基于PTN的差分服务和流量工程相结合的QoS方案.根据配电通信网中的具体业务在时延、带宽、可靠性等方面的不同要求,为各类业务提出QoS策略建议,从而构建具有高服务质量保障的配电通信网.以云南电网公司通信分公司PTN试验网为例,利用OPNET对网络时延、吞吐量和链路利用率进行仿真,结果表明使用PTN的QoS机制后,网络性能有很大提高.     

A QoS‐supported controlled burst retransmission scheme in OBS networks

Burst retransmission can reduce data loss in burst contention in optical burst switching (OBS) core nodes. However, uncontrolled burst retransmission may significantly increase the network load and data loss probability, defeating the purpose of retransmission. Therefore, controlled retransmission should be studied to achieve reasonable retransmission, particularly to support quality of service (QoS) in OBS networks in which priority traffic exists. In this paper, we develop a QoS‐supported controlled retransmission scheme in OBS networks. Different from previous works in the literature, we set a different value for the retransmission probability at each contention for both high‐ and low‐priority bursts, set different retransmission probabilities for bursts of different priorities for QoS support, and propose a retransmission analytical model for OBS networks. We take into account the load at each link due to both the fresh and the retransmitted traffic and calculate the path‐blocking probability and the burst loss probability for high‐priority and low‐priority bursts to evaluate the network performance. An extensive simulation is proposed to validate our analytical model. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

蓄意流量攻击下基于确定网络演算的互联电网自适应负荷频率控制策略

蓄意流量攻击通过抢占有限的网络带宽降低正常数据流的时效性。对于网络化负荷频率控制(load frequency control, LFC),流量攻击将造成稳定裕度下降、频率偏差幅度上升甚至越限事故。现有控制方案一般采用单一且固定的控制器保证最大攻击强度下的渐进稳定性,存在设计约束多、保守性大的缺点。因此提出了一种跟随攻击强度自适应调整控制器增益的LFC策略。首先,基于确定性网络演算,得到了无攻击场景下数据流传输延时上边界,并预设了一系列表征不同攻击强度的传输延时范围。其次,通过构造Lyapunov泛函,推导了针对每个攻击强度的控制器设计准则。最后,基于切换控制理论,确定了所提自适应方案所能容忍的最大攻击强度变化频率。仿真表明,与现有控制方案相比,所提方法的频率偏差幅度可下降12.60%,区域控制误差的绝对值误差积分可下降10.85%。     

多模式无线视频码流的传输与控制

采用快速传送协议/用户数据报协议/IP方式实现了多模式无线网络（WLAN、GPRS、CDMA）的码流传输,并完成无线通信下的RTCP双向控制信息链路.针对无线IP网络的传输特性,选取了适当的QoS参数反馈控制传输质量.实验测试表明,多模式无线通信系统下的码流传输在接收端取得了较好的视频传输质量.     

Decentralized model predictive‐based load‐frequency control in an interconnected power system concerning wind turbines

This paper presents a load‐frequency control (LFC) design using the model predictive control (MPC) technique in a multi‐area power system in the presence of wind turbines (WTs). In the studied system, the controller of each local area is designed independently such that the stability of the overall closed‐loop system is guaranteed. A frequency response model of the multi‐area power system including WTs is introduced, and physical constraints of the governors and turbines are considered. The model was employed in the MPC structures. Digital simulations for a two‐area power system are provided to validate the effectiveness of the proposed scheme. The results show that with the proposed MPC technique the overall closed‐loop system performance shows robustness in the face of uncertainties due to governor and turbine parameter variation and load disturbances. A performance comparison between the proposed controller with WTs and MPC without WTs and a classical integral control scheme is carried out, confirming the superiority of the proposed MPC technique with WTs. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Rate control for streaming media transmission over WLAN

In order to solve the problems of link layer retransmission and packet fragment strategies for IEEE 802.11, this paper proposes a variable packet TCPfriendly rate control (VPTFRC) scheme for streaming media transmission over wireless local area network (WLAN) by researching on the policy of packet size adjustment in transport layer based on the minimum retransmit-delay constraint. Unlike other proposals, this process considers the impact of wireless packet error ratio (PER) on the packet size adjustment and the performance of rate control. Simulation results demonstrate that our proposed process can simultaneously achieve higher throughput, better fairness, shorter transmission delay and less jitter than TFRC. Among them, the ratio of delay, jitter and packet loss rate can reach a maximum improvement ratio of 58%, 42% and 85% respectively. __________ Translated from Journal of Huazhong University of Science and Technology (Nature Science Edition), 2007, 35(1): 1–3 [译自: 华中科技大学学报(自然科学版)]     

Resource management in LEO satellite networks

To provide truly global coverage needed by increased Personal Communication Services (PCS), a new generation of mobile satellite networks has been proposed. These low Earth orbit (LEO) mobile satellite networks handle multimedia traffic and can be used for non-real-time as well as real-time service to remote areas. Due to the many handoffs, resource management and connection admission control are important tasks for fair bandwidth sharing and QoS guarantees. Because the total link capacity has to be divided among several carriers and given the limited buffer capacity of the ATM switch, resource management is vital. It ensures the ability of the network to provide users with their negotiated QoS while protecting the network and the end-systems from congestion. We introduced a simple connection admission control (CAC) priority policy based on the delay and cell loss requirements for the investigated types of traffic. We took into account the handoff status of the satellite beams involved. Thus, we propose an onboard buffer architecture with separated buffers for new calls and intra-satellite handoff calls. The priority scheme applied is as follows: highest priority is given to CBR, followed by rt-VBR, nrtVBR and ABR.     

基于QoS的变电站设备无线监测网络拓扑研究

随着无线传感器网络在智能变电站不同业务应用中的深化,网络的高数据率传输和网络的服务质量（qual-ity of service,QoS）问题成为无线传感器网络（wireless sensor network,WSN）的新热点。针对智能变电站的设备状态监测应用,利用无线传感器网络技术,建立分簇的三层智能变电站设备无线监测网络结构;参考 Zigbee协议和 IEC 61850报文规定,对监测网络数据流进行建模;从用户感知 QoS、网络 QoS 和节点 QoS 三个方面,结合Opnet仿真功能,提出包括端到端时延、MAC层时延、MAC层吞吐率、MAC层丢包率、数据碰撞、丢包率、比特误码率、信噪比和接收功率的QoS指标。根据实际变电站设备监测配置,建立起仿真网络模型,仿真研究表明相比于树状拓扑、Mesh拓扑网络,设计的簇状拓扑网络具有更好的QoS综合性能。     

QoS on LEO satellites

This paper discusses the role played by wireless network infrastructure in mobile commerce applications. The user's perception of service quality depends on the available resources and capabilities of the network. The new generation of low earth orbit (LEO) mobile satellite networks, deployed at altitudes ranging from 500 km to 2000 km, are well suited to handle multimedia traffic and to offer end-users equipped with hand-held devices at low cost-per minute access to network services. A wide range of multimedia services and applications are expected to provide users with QoS based asynchronous transfer mode (ATM) technology. LEO satellite networks provide significant wide area coverage, unique broadcast capability, ability to meet different QoS requirements, the ability to communicate with hand-held devices and low cost access. The main resources in the LEO networks are satellite radio bandwidth and the buffer capacity of the onboard ATM switch. The most important ATM resource management function is connection and call admission control. The real objective of this article is to introduce the general framework of resource reservation in multimedia LEO satellite networks which offers a unified approach to handle all the important aspects of resource reservation and radio-resource management functions required by E-commerce and mobile commerce applications.     

3层式广域保护系统通信网络

分析了3层式广域保护系统需要传输的消息种类以及各类消息对通信系统的要求,在此基础上选择了IP over ATM over SDH作为网络类型,以充分利用同步数字体系（SDH）光纤自愈环的低时延和可靠性以及异步传送模式（ATM）的服务质量（QoS）和IP的多业务支持;设计了多环网络拓扑并探讨了关键消息传输的通信协议;使用OPNET Modeler对关键信息传输进行了仿真,证实了此通信系统的有效性,仿真结果表明该通信系统可以满足最恶劣情况下的实时性和可靠性要求。     

Adaptive bandwidth framework for provisioning connection-level QoS for next-generation wireless cellular networks

The next generation of wireless cellular networks is expected to support real-time multimedia services with different classes of traffic and diverse bandwidth requirements. Bandwidth is a scarce resource in wireless networking that needs to be carefully allocated amid competing connections with different quality of service (QoS) requirements. In this paper, an adaptive framework for supporting multiple classes of multimedia services with different QoS requirements in wireless cellular networks is proposed. The framework combines the following components: (1) a threshold-based bandwidth allocation policy that gives priority to handoff calls over new calls and prioritizes among different classes of handoff calls by assigning a threshold to each class; (2) an efficient threshold-type call admission control (CAC) algorithm; and (3) a bandwidth adaptation algorithm (BAA) that dynamically adjusts the bandwidth of ongoing multimedia calls to minimize the number of calls receiving lower bandwidth than they had requested. Numerical results show that the proposed adaptive multimedia framework outperforms existing non-adaptive schemes in terms of the handoff call dropping probability and effective utilization.     

WLAN中吞吐量异构下最小竞争窗口自适应算法

随着移动设备的增多,基于802.11协议的 WLAN系统已经被越来越广泛地使用。由于802.11协议是基于吞吐量相等的设计模式,在这种模式下所有的用户(包括AP)的吞吐量都相等。但是在实际的WLAN系统中,下行吞吐量往往大于上行吞吐量,因此 WLAN设计模式在现实应用中会阻塞下行数据包的传输,上下行吞吐量异构已经是需要解决的一个重要问题。文中提出了一种自适应调节 AP和 STA的最小退避窗口的算法,解决了上下行流量异构问题。     

CMT‐CQA: Cross‐layer QoS‐aware adaptive concurrent multipath data transfer in heterogeneous networks

Stream control transport protocol (SCTP)‐based concurrent multipath transfer (CMT) can help multi‐homed devices to increase their throughput by making use of parallel transmissions over multiple paths and bandwidth aggregation. However, if CMT cannot identify wireless error, it cannot really achieve the desired performance. Furthermore, if CMT only utilizes all available paths for data delivery, it will undoubtedly degrade application‐level performance since the asymmetric paths may involve large quality differences. This paper proposes a novel cross‐layer quality‐of‐service (QoS)‐aware adaptive CMT (CMT‐CQA) with the following aims: (i) to provide an adaptive ‘CMT‐to‐partial CMT’ adjustment strategy for efficient bandwidth aggregation by jointly considering transport layer QoS, MAC layer QoS, and path history information; (ii) to address an enhanced congestion window (cwnd) fast recovery mechanism to reduce bursty transmission in multi‐homed wireless network environments where fail‐over occurs frequently; and (iii) to introduce a proper multimedia transmission behavior to improve users' quality of experience (QoE) for multimedia streaming service. Simulation results show that CMT‐CQA outperforms the existing CMT solutions in terms of performance and QoS. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Adaptive TS‐FNN control for a class of uncertain multi‐time‐delay systems: The exponentially stable sliding mode‐based approach

This paper presents an adaptive Takagi–Sugeno fuzzy neural network (TS‐FNN) control for a class of multiple time‐delay uncertain nonlinear systems. First, we develop a sliding surface guaranteed to achieve exponential stability while considering mismatched uncertainty and unknown delays. This exponential stability result based on a novel Lyapunov–Krasovskii method is an improvement when compared with traditional schemes where only asymptotic stability is achieved. The stability analysis is transformed into a linear matrix inequalities problem independent of time delays. Then, a sliding mode control‐based TS‐FNN control scheme is proposed to achieve asymptotic stability for the controlled system. Since the TS‐FNN combines TS fuzzy rules and a neural network structure, fewer numbers of fuzzy rules and tuning parameters are used compared with the traditional pure TS fuzzy approach. Moreover, all the fuzzy membership functions are tuned on‐line even in the presence of input uncertainty. Finally, simulation results show the control performance of the proposed scheme. Copyright © 2008 John Wiley & Sons, Ltd.     

无线Mesh网络在输电线状态监测系统中的应用

文章针对输电线状态监测系统的要求,结合无线Mesh网络的特点,提出了一种应用无线Mesh网络构建输电线状态监测通信系统的方案.该方案实现了无光纤接入条件下,线路状态监测数据的高速、安全可靠传输,利用Mesh网络的多跳特性实现了监测数据的远距离传输.     

Free‐weighting matrices‐based robust wide‐area FACTS control design with considering signal time delay for stability enhancement of power systems

This paper presents a free‐weighting matrix (FWM) method based on linear control design approach for the wide‐area robust damping (WARD) controller associated with flexible AC transmission system (FACTS) device to improve the dynamical performance of the large‐scale power systems. First, the linearized reduced‐order plant model is established, which efficiently considers the time delay of the remote feedback signals transmitted by wide‐area measurement systems. Then, based on the robust control theory, the design of the FACTS‐WARD controller is formulated as the standard control problem on delay‐dependent state‐feedback robust control, which is described by a set of linear matrix inequality constraints. Furthermore, in order to obtain the optimal control parameters that can endure the maximum time delay, a FWM approach is proposed to solve the time‐dependent problem of the time‐delay system. Meanwhile, an iterative algorithm based on cone complementary linearization is presented to search out the optimal control parameters. Finally, the nonlinear simulations on the 2‐area 4‐machine and the 5‐area 16‐machine test systems are performed, to evaluate the control performance of the proposed robust wide‐area time‐delay control approach. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Low‐latency retransmission control in a wireless communication system for plant instrumentation and control

When wireless communication technology is applied to plant instrumentation and control systems, it is important to ensure real‐time transmission and high reliability of the wireless communication system. However, the wireless communication system is prone to more frequent occurrence of transmission errors than a wired communication system, so that generally retransmission is implemented generically. To reduce retransmission latency, we propose a method of low‐latency retransmission control, which is a data block transmission method with multi‐redundant media access control layer (MAC) headers, to implement a wireless communication system for plant instrumentation and control. We carried out system tests using prototypes with the proposed methods, that is, data block transmission with multi‐redundant MAC headers. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Predictive call admission control for multimedia streaming in CDMA cellular environments

Third-generation (3G) wireless networks based on code-division multiple access (CDMA) have been engineered to provide mobile users with voice as well as advanced packet data services. Support of Internet-based multimedia streaming services is considered a critical factor for future deployment of such networks. Provisioning streaming services in a dependable way, however, requires supporting data transmission at relatively high data rates while maintaining session quality during both intracell and intercell user movements. In this paper, an adaptive bandwidth allocation and admission control scheme is proposed for managing network resources for a streaming service. Streaming requests are assumed to be served by an adaptive server capable of choosing suitable video streaming parameters (e.g., video resolution, frame rate, and encoding parameters) in response to possible requests from the wireless network to vary the currently allocated bandwidth. The devised admission control scheme exploits a priori knowledge of user mobility patterns to minimize the risk of running into an overload condition after acceptance of a new multimedia streaming connection. The obtained simulation results show that, compared to a nonpredictive admission control scheme, the proposed scheme achieves a lower forced-termination probability and higher throughput, while consuming less base-station transmission energy.