基于优先级的IEEE802.16系统接纳控制算法研究

鉴于IEEE802.16标准中未对接纳控制机制提出定义,为了提高系统带宽利用率,在分析现有无线网络接纳控制技术的基础上,结合IEEE802.16的具体机制提出了一种基于业务优先级的接纳控制算法。相比于先到先服务的接纳机制,该算法严格区分业务优先级,为不同优先级业务预留带宽,以保证实时业务的服务质量(QoS)要求。利用NS2网络模拟软件对算法进行了仿真和性能评估。结果表明,本接纳控制算法可以较好地保障高优先级业务的实时性,同时在重负载情况下系统带宽利用率有了明显提高。     

无线Ad Hoc网络支持QoS的路由协议研究

当前,Ad Hoc网络传输多媒体业务需求提出了服务质量（QoS）的要求。由于Ad Hoc网络本身具有分布式控制、无线信道容量受限以及节点、链路和网络拓扑状态不断变化等特点,使其相对于固定无线网络及有线网络提供有保证且稳定的QoS要困难得多。文章总结了当前DSR协议的QoS研究进展,对不同的改进方案加以分类比较,指出了存在的问题：并针对hdHoc网络中基于资源预留的QoS算法所带来的复杂度问题,提出了适合该网络的测量可用带宽算法,构造了一种支持实时业务的Ad Hoc网络QoS服务机制。     

多媒体业务在越区切换中服务质量保证方法的研究

为了降低多媒体业务在移动环境中的呼叫中断率,提高无线信道的利用率,该文提出了一种动态预留带宽分配机制(DRBA),该机制对到达的越区切换呼叫按业务类型区别处理,对于高优先级的实时业务,通过在邻近小区内预留带宽的方法降低呼叫中断率;对于非实时业务,当小区内的信道带宽不足以支持新到达的越区切换呼叫时,通过动态地借用实时业务过度预留的带宽,改善非实时业务的呼叫中断率,进一步达到提高无线信道利用率,为不同的业务类型提供公平的服务质量(QoS)的目标。     

基于多门限预留机制的自适应带宽分配算法

针对异构无线网络融合环境提出了一种基于多门限预留机制的自适应带宽分配算法,从而为多业务提供QoS保证。该算法采用多宿主传输机制,通过预设各个网络中不同业务的带宽分配门限,并基于各个网络中不同业务和用户的带宽分配矩阵,根据业务k支持的传输速率等级需求和网络状态的变化,将自适应带宽分配问题转化为一个动态优化问题并采用迭代方法来求解,在得到各个网络中不同业务和用户优化的带宽分配矩阵的同时,在带宽预留门限和网络容量的约束条件下实现网络实时吞吐量的最大化,以提高整个异构网络带宽的利用效率。数值仿真结果显示,所提算法能够支持满足QoS需求的传输速率等级,减小了新用户接入异构网络的阻塞概率,提高了平均用户接入率并将网络吞吐量最大提高40%。     

基于博弈论的移动WiMAX接纳控制

移动WiMAX是一种重要的宽带无线接入技术,它具有数据传输率高、覆盖范围广、支持多种数据业务等优点。为了保证不同业务的QoS,该文提出一种基于博弈论的接纳控制算法。该算法首先给不同的业务赋予不同的优先级,然后建立一个非合作二人博弈模型,通过求解纳什均衡决定是否接纳连接请求,以及带宽的预留方案。仿真结果表明,该算法能够提高带宽的利用率,降低新发起连接的阻塞概率和切换连接的丢弃概率,并且能给不同业务提供区分服务。     

CDMA2000 EV-DO系统接纳控制算法研究

文中基于CDMA2000 EV-DO系统,对通信系统接纳控制算法进行了研究.首先介绍了接纳控制在CDMA系统中的重要作用.然后研究了基于QoS的接纳控制判决条件,分析了在增加新的QoS流和切换过程中的系统资源预留打开条件.通过仿真方法分析了各种QoS流与BE流之间占用扇区带宽的换算,继而研究了基于扇区带宽的接纳控制算法.运用色阶的方式,介绍了一种CPU利用率的控制方法,研究了在不同CPU利用率的情况下的接纳控制算法.最后提出了两种基于扇区用户数的接纳控制算法,并分析了各自的特点.     

基于无线Mesh网络的分布式协调功能的研究

随着无线mesh网络的迅速发展和实时多媒体业务的日益增长,要求无线网络不仅能提供简单的连通性,还需要提供非常有效的QoS保证机制,针对这一问题,以时分多址/时分双工(TDMA/TDD)技术为基础,提出一种基于无线mesh网络的分布式协调功能,信道存取与数据传输发生在不同的时隙中,能够为端到端数据流公平的分配带宽,并且保证了实时服务传输的QoS.仿真及分析表明该协调功能可提高系统吞吐量并降低端到端延迟,有着更好的QoS性能.     

IP电话接入端QoS服务的设计与实现

IP电话系统的业务是实时业务，对延迟、抖动等因素十分敏感，而IP网络本身并不提供QoS服务，所以QoS服务实现是IP电话系统必须研究的内容。本文在新一代电话体系结构的基础上设计了一个带控器来控制H.323zone的出口带宽资源，以提供端QoS服务。从而带控器与主干QoS服务一起构成IP电话系统的端到端QoS服务系统。     

IP QoS研究的现状与发展趋势

目前，随着电信业务的引入，IP网的服务质量（IP QoS）成为下一代Internet的重要研究课题。由于IP协议的无连接特性和IP网络松散的控制管理方式，使这项研究面临很大的挑战。IPQoS的研究范围十分广泛，不仅包含路由和业务流量控制，还涉及到网络管理、计费和网络测量。当前主要的IP QoS技术集成服务（IntServ）集成服务的基本思想是在传送数据之前，根据业务的QoS需求进行网络资源预留，从而为该数据流提供端到端的QoS保证。资源预留协议（RSVP）是集成服务的核心。这是一种信令协议，用来通知网络节点预留资源。如果资源预留失…     

IEEE802．11eWLAN中基于HCCA机制的带宽分配算法的研究

随着使用WLAN（无线局域网）接入因特网的日渐普及,IEEE802．11eWLAN中的HCCA（混合控制信道接入）机制由于在处理实时多媒体业务的高效率受到越来越广泛的关注。在WLAN中为达到高带宽利用率和良好的端到端QoS,介绍了一种基于HCCA机制的带宽分配算法,同时对该算法与802．11PCF（点协调功能）两种接入场景下的网络性能进行仿真比较,其结果验证了该算法可以为WLAN提供良好的QoS保证,对在WLAN中传输语音、视频等实时业务具有一定的指导意义。     

Radio resource management for cellular CDMA systems supporting heterogeneous services

A novel radio resource management (RRM) scheme for the support of packet-switched transmission in cellular CDMA systems is proposed by jointly considering the physical, link, and network layer characteristics. The proposed resource management scheme is comprised of a combination of power distribution, rate allocation, service scheduling, and connection admission control. Power distribution allows individual connections to achieve their required signal-to-interference-plus-noise ratio, while rate allocation guarantees the required delay/jitter for real-time traffic and the minimum transmission rate requirement for non-real-time traffic. Efficient rate allocation is achieved by making use of the randomness and burstiness; of the packet generation process. At the link layer, a packet scheduling scheme is developed based on information derived from power distribution and rate allocation to achieve quality of service (QoS) guarantee. Packet scheduling efficiently utilizes the system resources in every time slot and improves the packet throughput for non-real-time traffic. At the network layer, a connection admission control (CAC) scheme based on the lower layer resource allocation information is proposed. The CAC scheme makes use of user mobility information to reduce handoff connection dropping probability (HCDP). Theoretical analysis of the grade of service performance, in terms of new connection blocking probability, HCDP, and resource utilization, is given. Numerical results show that the proposed RRM scheme can achieve both effective QoS guarantee and efficient resource utilization.     

Measurement-Based Admission Control at Edge Routers

It is very important to allocate and manage resources for multimedia traffic flows with real-time performance requirements in order to guarantee quality of service (QoS). In this paper, we develop a scalable architecture and an algorithm for admission control of real-time flows. Since individual management of each traffic flow on each transit router can cause a fundamental scalability problem in both data and control planes, we consider that each flow is classified at the ingress router and data traffic is aggregated according to the class inside the core network as in a DiffServ framework. In our approach, admission decision is made for each flow at the edge (ingress) routers, but it is scalable because per-flow states are not maintained and the admission algorithm is simple. In the proposed admission control scheme, an admissible bandwidth, which is defined as the maximum rate of a flow that can be accommodated additionally while satisfying the delay performance requirements for both existing and new flows, is calculated based on the available bandwidth measured by edge routers. The admissible bandwidth is a threshold for admission control, and thus, it is very important to accurately estimate the admissible bandwidth. The performance of the proposed algorithm is evaluated by taking a set of simulation experiments using bursty traffic flows.     

A Simple Analytical Model for Expected Frame Waiting Time Evaluation in IEEE 802.11e HCCA Mode

IEEE 802.11e standard defines two access modes to provide Quality of Service support for 802.11-based Wireless LANs: Enhanced Distributed Channel Access and HCF Controlled Channel Access (HCCA). Only HCCA can guarantee bandwidth per flow which is suitable for various multimedia application requirements. However, the reference scheme HCCA is designed without awareness of variable bit rate (VBR) transmission. Several enhancement techniques have been proposed to address the VBR problem, but there are few research results for a model to capture the characteristics of HCCA. In this paper, an analytical model for the expected packet waiting time is proposed. The model can capture the system behavior per session leading to suitable admission control process for VBR support. The proposed model has been validated using the Network Simulator. The results confirm that the reference admission control scheme with mean data rate acceptance cannot guarantee the required bound on waiting time. Using the model, suitable parameters can be investigated for admission control with VBR support. The model can also be applied with polling based technologies, such as WiMAX.     

Enhancing Design of Visual-Servo Delayed System

A robust adaptive predictor is proposed to solve the time-varying and delay control problem of an overhead crane system with a stereo-vision servo. The predictor is based on the use of a recurrent neural network (RNN) with tapped delays, and is used to supply the real-time signal of the swing angle. There are two types of discrete-time controllers under investigation, i.e., the proportional-integral-derivative (PID) controller and the sliding controller. Firstly, a design principle of the neural predictor is developed to guarantee the convergence of its swing angle estimation. Then, an improved version of the particle swarm optimization algorithm, the parallel particle swarm optimization (PPSO) method is used to optimize the control parameters of these two types of controllers. Finally, a homemade overhead crane system equipped with the Kinect sensor for the visual servo is used to verify the proposed scheme. Experimental results demonstrate the effectiveness of the approach, which also show the parameter convergence in the predictor.     

一种用于提供QoS保证的准入控制方法

本文推导了ON/OFF马尔可夫数据流的资源分配与延迟分布、丢失率的关系,在此基础上进行可准入性测试,并根据流的优先权大小给出一种优化的准入控制方法,可为各类流提供服务质量(QoS)保证.最后通过算例说明该方法的有效性.     

Optimal Scheduling for Minimum Delay in Passive Star Coupled WDM Optical Networks

In this paper, a local optimization framework is proposed, which is able to include system constraints including channel availability, receiver availability and tuning overhead by linear mathematical formulations so that it is sufficient to obtain the optimal performance in terms of message delay. A mixed integer linear programming (MILP) based scheme for passive star coupled WDM optical networks is presented. Based on the new solution, the wavelength assignment and message sequence that guarantee the delivery of the given traffic request, while minimizing the average delay can be achieved. Moreover, the negative effect of the tuning overhead has been incorporated into the new algorithm, which has been ignored in most of the previous work. Numerical results obtained suggest that the proposed scheme is a promising approach for optimizing the network performance in terms of average message delay.     

Single phase admission control for QoS-routing protocol in ad hoc networks

In this paper, in order to fulfill real-time traffic requirements in ad hoc networks, a novel and effective single phase admission control (SPAC) scheme for QoS-routing protocols has been proposed. The SPAC scheme is based on the ad hoc on-demand distance vector (AODV) protocol with slight modifications of control packets; network congestions are avoided by a simple and precise admission control that blocks most of the overloading flow requests in the route-discovery process. System simulations show that the SPAC scheme and its performance is comparable to the contention-aware admission control protocol (CACP)-Multihop performance in all respects; the SPAC scheme is also simpler. As compared to a QoS-aware routing protocol employing either “listen” or “hello” scheme, the SPAC protocol offers higher throughput and remarkably less end-to-end delays under heavy loads.     

一种面向实时业务的Ad Hoc网络MAC协议

为降低AdHoe网络中实时业务的端到端时延,提出了基于802．11DCF的改进协议。协议采用3种机制降低实时业务的时延：面向路径的连续转发机制将RTS中的转发信息携带在ACK中发送,给实时业务提供较高的接入优先级;标签交换机制使得中间节点可以在MAC层获取转发信息,加快了实时业务数据包的转发速度;重传控制机制减少了无效传输的超时数据包。仿真结果表明,在重负载条件下,改进协议中实时业务的时延比802．11DCF有大幅度的下降,网络吞吐量也有所提高。     

Design of the QoS framework for the IEEE 802.16 mesh networks

IEEE 802.16 (WiMax) technology is designed to support broadband speeds over wireless networks for the coming era of broadband wireless access (BWA). IEEE 802.16 is expected to provide transmission of high‐rate and high‐volume multimedia data streams for fixed and mobile applications. As an extension of point‐to‐multipoint (PMP) configuration, the IEEE 802.16 mesh mode provides a quicker and more flexible approach for network deployment. Multimedia networking requires quality‐of‐service (QoS) support, which demands elaborate mechanisms in addition to the four service types defined in the specification. By examining standard centralized and distributed scheduling/routing schemes in the mesh mode from QoS aspect, a BS‐controlled and delay‐sensitive scheduling/routing scheme is proposed in the paper. Associate mechanisms including admission control, flow setup and link state monitoring are also proposed. Integration of the proposed mechanisms is presented as a complete QoS framework. Simulation study has demonstrated that the average delay as well as the delay jitters per hop in the proposed scheme is smaller than that of the distributed scheme and much smaller than that of the centralized scheme. Furthermore, proposed mechanisms can also achieve higher throughput than the contrasts and generate much smaller signaling overhead, making the proposed framework a promising scheme for multimedia support in the IEEE 802.16 mesh network. Copyright © 2009 John Wiley & Sons, Ltd.