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.     

A QoS control scheme using dynamic window size control for wide area ubiquitous wireless network

This paper describes a quality‐of‐service (QoS) control scheme for a wide‐area ubiquitous wireless network which is designed to accommodate many wireless terminals (WTs), such as sensors and actuators, in a large cell area. The purpose of this paper is to establish a QoS control scheme in a medium access control (MAC) layer that can hold the transmission delay of high‐priority class traffic within a predefined value regardless of how much low‐priority class traffic there is. Several QoS control schemes for wireless communication use have been proposed. However, in the wide‐area ubiquitous wireless network, an access point (AP) accommodates many WTs and the AP traffic volume often drastically changes. Therefore, conventional schemes sometimes cannot control the QoS of high‐priority traffic. To solve this problem, we propose a QoS control scheme that calculates a suitable initial back‐off window size of random access for each QoS class by using equations derived from a Markov chain behavior model. The proposed scheme adjusts the window size so as to prevent increased transmission delay of high‐priority traffic. The scheme's performance is clarified by computer simulation. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

基于自适应编码和调制技术的802.16调度算法

IEEE 802.16标准具有面向连接的特性,能够为每个连接提供QoS保证.标准定义了QoS架构中BS与SS间交换信息的信令机制,但是并没有规定上行带宽分配的调度算法,而这正是目前802.16领域研究的热点.对于VoIP、流媒体等实时业务来说,其对延迟和延迟抖动非常敏感.针对这一情况,本文提出了一种调度算法,利用自适应编码和调制技术,通过动态变化调制和编码方式,以牺牲一定的传输速率为代价来保证链路的稳定工作.即使在无线网络状态不佳的情况下,连接的QoS需求也能得到保证,从而改善了实时业务的运行状况.     

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.     

基于3G物联网的高压输电线路多状态信息监测系统

开发了一种基于3G物联网技术的综合数字化图像监控及运行状态参数监控等多种监测方法于一体的输电线路多状态信息监测系统,系统将图像信号、传感器采集的设备状态信号进行数字化,通过3G无线通信网络实时传输至多种移动接入终端,从而实现高压输电线路多状态信息监测。系统设计分为数据采集终端层、3G传输层、专家分析控制系统层3层结构,其中3G传输层采用自适应带宽的3G无线数据传输技术,充分利用中国电信、中国联通、中国移动3G网络,通过软件自动切换3种网络中信号较好的1个网络,根据多条链路的带宽,自动分配音视频数据以及设备运行状态数据的带宽,大大增加了网络通信带宽,提高了视频、音频的传输质量,保证了输电线路监测系统的稳定性、可靠性、实时性。     

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。     

一种有效的802.16 BWA系统MAC层QoS框架

IEEE 802.16系列标准定义了WiMAX的无线空中接口,尽管标准详细的定义了MAC层信号机制,但并没有一套完整的资源管理调度机制,而资源管理和调度是影响QoS性能的重要部分.本文首先简要介绍了IEEE 802.16协议,分析了其QoS机制的主要内容,包括带宽的请求分配机制,准人和调度机制等.然后提出了一套有效的QoS框架,主要包括准入控制策略和上行调度策略.为了让不同业务的QoS得到保证,文章重点探讨了多优先级公平队列算法(MPFQ),通过这套机制,可以为不同级别的业务提供不同等级的Qos服务.     

Cross-Layer Design of Dynamic Bandwidth Allocation in DVB-RCS

In this paper, a novel cross-layer framework for optimizing the dynamic bandwidth allocation (DBA) of a digital video broadcast (DVB)-return channel satellite (RCS) system using adaptive coding is proposed. The design of the medium access control (MAC) methods taking into account the adaptive physical layer and higher layers' quality of service (QoS) requirements is cast as an optimization problem by using the network utility maximization (NUM) framework applied within the satellite subnetwork. Hierarchical and global solving procedures fully compliant with the DVB-RCS standard are proposed. They do not only provide minimum bandwidth guarantees but also maximize fairness. Further, they allow a joint optimization of the time slot size and overall system efficiency while minimizing signalling overhead. A reduced computational complexity algorithm to solve the DBA problem is presented. In practical terms, it increases the number of connections with absolute and relative QoS requirements the system can manage and facilitates the interoperability of the satellite network within an Internet protocol (IP) environment.     

Sliding mode disturbance observer‐based adaptive control for uncertain MIMO nonlinear systems with dead‐zone

In this paper, an adaptive integral sliding mode control (ISMC) scheme is developed for a class of uncertain multi‐input and multi‐output nonlinear systems with unknown external disturbance, system uncertainty, and dead‐zone. The research is motivated by the fact that the ISMC scheme against unknown external disturbance and system uncertainty is very important for multi‐input and multi‐output nonlinear systems. The system uncertainty, the unknown external disturbance, and the effect of dead‐zone are integrated as a compounded disturbance, which is well estimated using a sliding mode disturbance observer (SMDO). Then, the adaptive ISMC based on the designed SMDO is presented to guarantee the satisfactory tracking performance in the presence of system uncertainty, external disturbance, and dead‐zone. Finally, the designed adaptive ISMC strategy based on SMDO is applied to the attitude control of the near space vehicle, and simulation results are presented to illustrate the effectiveness of the proposed adaptive ISMC scheme using the SMDO. Copyright © 2016 John Wiley & Sons, Ltd.     

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.     

A novel and effective multi-constrained QoS routing scheme in WMNs

Multi-constrained quality of service (QoS) routing aims at finding an optimal path that satisfies a set of QoS parameters, as an NP complete problem, which is also a big challenge for wireless mesh networks (WMNs). Heuristic algorithms with polynomial and pseudo-polynomial-time complexities are often used to deal with this problem. However, existing solutions, most of which suffered either from excessive computational complexities or from low performance, were proposed only for wired networks and cannot be used directly in wireless mesh networks. In this paper, we propose a novel routing scheme based on mean field annealing (MFA-RS) to solve this problem. MFA-RS first uses a function of two QoS parameters, wireless link’s delay and transmission success rate as the cost function, and then seeks to find a feasible path by MFA. Because MFA-RS uses a set of deterministic equations to replace the stochastic process in simulated annealing (SA) and uses saddle point approximation in the calculation of the stationary probability distribution at equilibrium, the convergence time is much less than the routing scheme based on SA (SA-RS). Simulation results demonstrate that MFA-RS is an effective algorithm and is very fit for WMNs.     

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.     

Decentralized adaptive multi‐dimensional Taylor network tracking control for a class of large‐scale stochastic nonlinear systems

This paper investigates the problem of adaptive multi‐dimensional Taylor network (MTN) decentralized tracking control for large‐scale stochastic nonlinear systems. Minimizing the influence of randomness and complex nonlinearity, which increases computational complexity, and improving the controller's real‐time performance for the stochastic nonlinear system are of great significance. With combining adaptive backstepping with dynamic surface control, a decentralized adaptive MTN tracking control approach is developed. In the controller design, MTNs are used to approximate nonlinearities, the backstepping technique is employed to construct the decentralized adaptive MTN controller, and the dynamic surface control technique is adopted to avoid the “explosion of computational complexity” in the backstepping design. It is proven that all the signals in the closed‐loop system remain bounded in probability, and the tracking errors converge to a small residual set around the origin in the sense of a mean quartic value. As the MTN contains only addition and multiplication, the proposed control method is more simplified and of good real‐time performance, compared with the existing control methods for large‐scale stochastic nonlinear systems. Finally, a numerical example is presented to illustrate the effectiveness of the proposed design approach, and simulation results demonstrate that the method presented in this paper has good real‐time performance and control quality, and the dynamic performance of the closed‐loop system is satisfactory.     

交换路由技术在调度自动化主站网络中的应用

概述了电力调度自动化主站目前常用的计算机网络组网方式。介绍了采用交换路由及相关网络技术，如服务质量（QoS）、虚拟局域网（VLAN）、第3层交换和第4层交换技术，来提高SCADA/EMS数据传输的实时性和安全性的经验。VLAN技术将整个主站计算机网络分成采集子网、Web网，并在主网、子网之间利用交换机的第3层路由功能进行通信；利用第3层交换机的访问列表控制功能来限制数据的非法访问，增强网络的安全性；利用QoS技术对网络中的数据流按优先级别高低分配带宽，实现实时性较强的数据优先通信。     

Wavelength‐transparent IP‐over‐CWDM network with stackable ROADMs for best effort performance

Stackable reconfigurable optical add/drop multiplexers (S‐ROADMs) have been proposed for use in IP over coarse wavelength‐division multiplexing (CWDM) networks so as to provide capabilities of remote lightpath reconfiguration and manual ROADM reconfiguration under the best effort transmission specified by the service level agreement. The S‐ROADM can be constructed by connecting modules with different wavelengths required in the node. The experimental results clarify that the S‐ROADM can add/drop or pass through the wavelengths successfully, providing no limit to the passing‐through (PT) wavelengths, that is, ensuring the wavelength transparency in the network. The S‐ROADMs could remove congestions by adding a lightpath remotely within a recovery time with degraded SLA. The transmission break time was also within the recovery time when adding a module manually to the in‐service S‐ROADM to increase bandwidth to be provided to new users. As a result, the S‐ROADMs provide more flexible CWDM networks in terms of scalability and reconfigurability. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A methodology to design continuous‐time adaptive equalizers

Serial communications systems suffer from channel bandwidth limitations that result in eye closure and inter‐symbol interference. Adaptive equalization at the receiver is widely implemented to alleviate this, and a number of continuous‐time techniques aiming multi‐gigabit operation have been proposed. The operation of adaptive equalizers is based on signal filtering carried out by loop filters whose characteristics are usually given ad‐hoc after a trial and error process. This paper presents a unified analysis of the operation of continuous‐time adaptive equalizers that results in a general design methodology to select the frequency characteristics of the filters implemented in the adaptation loop. Using the proposed methodology, a novel adaptation loop filter combination incorporating two low‐pass filters is presented. Copyright © 2016 John Wiley & Sons, Ltd.     

基于WMAN的馈线快速保护实时性研究

利用纵联保护原理可以很好地解决馈线间多开关的保护定值配合问题,实用的关键是保护通信的成本.馈线快速保护对通信的实时性要求相对较低,因此可以考虑采用低成本但实时性较差的无线通信技术.提出一种宽带无线城域网(WMAN)技术的实现方案,重点对该通信方案的延时进行了分析.研究表明,通过完善网络协议,可以满足馈线快速保护的实时性要求.该方案通信的延时主要是无线网络物理层和媒体访问控制(MAC)层延时.其中,物理层延时比较确定,选择合适的标准帧长就可以满足要求:MAC层延时具有很大的不确定性,主要是带宽申请和服务调度的延时,但如果建立专门的带宽申请时隙,并将保护信息作为最高优先级服务,其延时也可以控制在较短时间.仿真计算结果证明该方案总延时在100 ms之内.