基于多面体的分布式WiMAX Mesh网络带宽调度算法

在轮询带宽调度和随机带宽调度两种经典算法的基础上,提出一种基于多面体优先列表的带宽资源调度算法来分析和优化WiMAX网络Mesh模式的带宽请求和调度过程.该算法通过为各个用户站构建不同的静态优先请求次序,避免或者减少了"带宽资源分配不均"现象,使带宽资源能够在网络局部得到优化调度,并扩展到整个无线网络.分析和仿真结果表明,本算法能够极大地改善整个网络的运行性能.     

WiMAX网络PMP模式带宽分配过程研究

对IEEE 802.16网络点对多点模式的带宽分配过程进行分析,讨论在不同可用带宽情况下WiMAX网络中各种数据流通过用户站向基站请求带宽资源的过程以及基站和用户站对网络中的不同数据流的带宽请求进行处理的情况.在此基础上,提出一种分析WiMAX网络按用户站集中分配带宽资源的马尔可夫模型.该模型使用多重队列的方式分析了基站和用户站的运行情况,提供了在不同网络配置情况下或者使用不同带宽分配算法时网络中各种数据流的阻塞概率,为分析WiMAX网络带宽资源分配过程和优化网络参数设置提供帮助.     

基于队列长度的上行资源调度性能分析及策略

对无线通信网络上行队列调度进行了分析和设计.提出一种基于队列长度的上行资源调度策略,建立了数学模型,采用双随机泊松过程模型,对上行资源调度进行了理论分析,推导提出了衡量调度性能的参数:延时和带宽利用率.将该策略应用于基于IEEE 802.16d的无线网络,数值分析和仿真结果表明,所提算法能对上行资源进行优化配置,实现系统所需的QoS服务.     

认知无线网络中的跨层资源优化

跨层资源优化是设计认知无线网络重要的一环,是典型的多目标优化问题。为此,提出一种自适应克隆与邻域选择优化算法解决认知无线网络中的资源优化分配问题。以使用带宽、消耗功率、数据传输速率等指标作为认知网络优化目标,并将其在算法中进行优化。通过2种典型测试函数的仿真比较,结果表明该算法能够有效解决认知无线网络中的频谱资源分配、功率控制及速率提升等多目标优化问题,且与SPEA-2算法和NNIA算法相比,具有明显的优越性。     

Optimized collaborative filtering recommendation based on users' interest degree and feature

协同过滤技术目前被广泛应用于个性化推荐系统中.为了使用户的最近邻居集合更加精确有效,提出了基于用户兴趣度和用户特征的优化协同过滤推荐算法.首先通过计算用户对项目的兴趣度来对用户进行分组;然后采用贝叶斯算法分析出用户具有不同特征时对项目的喜好程度;最后采用一种新的相似度度量方法计算出目标用户的最近邻居集合.实验表明该算法提高了最近邻居集合的有效性和准确度,推荐质量较以往算法有明显提高.     

异构无线网络环境下的联合网络选择策略

异构无线网络环境下,无线终端可以采用多种接入技术(UMTS、LTE、WLAN等)进行通信.针对异构无线网络中带宽资源受限的问题,提出了一种基于带宽资源分配的网络选择策略.该策略首先以用户的信息传输速率作为目标函数,以带宽资源限制作为约束条件,采用凸优化理论得到最大化的信息传输速率,然后根据获得最大化信息传输速率所需的带宽资源和接入网络可提供的带宽资源,将用户分配到最合适的网络中,可以避免盲目接入造成的资源浪费.与已有的网络选择策略不同,提出的策略以带宽受限情况下最大化整体网络的信息传输速率和带宽利用率为目标.理论分析和仿真实验证明该文提出的网络选择策略可以获得较高的网络吞吐量和资源利用率.     

一种基于节点可选度的P2P点播流媒体数据调度算法

当前的P2P(Peer-to-Peer)点播流媒体系统中数据调度算法未能充分利用每个用户节点自身的特性.在分析典型数据调度算法基础上提出一种基于节点可选度的数据调度算法(SSP算法).该算法一方面在调度下载数据块时综合考虑了邻居节点带宽能力及其所拥有的数据信息.另一方面对服务节点的请求处理过程进行了优化.SSP算法有利于提高用户节点播放视频的连续性,降低流媒体服务器的负载压力,从而改善P2P点播流媒体系统的整体服务质量.仿真结果和实际应用表明算法性能良好,适用于用户节点能力差异较大的P2P点播流媒体环境.     

基于模数的WiMAX网络高负载自适应冲突解决算法

根据现有的部分研究结果发现,IEEE 802.16标准中使用的截断二进制指数后退算法在解决网络冲突时效率很低;并且当网络的负载增多时,该算法的运行性能更差.在此基础上,提出了一种基于模数的自适应冲突解决算法来优化WiMAX网络的冲突解决过程.该算法将所有用户站按照当前时间帧内的传输机会数量分为多个小组,并且要求用户站只能通过特定的传输机会发送请求.与此同时,为了保证整个网络的高性能,本算法要求基站和用户站根据上一轮请求过程中的平均冲突概率和传输机会使用率来调整当前时间帧内的传输机会数量,以及挑选部分用户站参与带宽请求,保证了WiMAX网络在高负载情况下的运行性能.模拟结果表明,本算法在WiMAX网络运行过程中能够较好地解决请求过程中的冲突,对网络性能提高较大.     

舰艇编队重叠子网联合无线资源调度算法

无线资源调度技术是无线网络对用户提供服务质量保障的关键。层次分析的跨异构子网联合无线资源调度算法以编队通信需求为基础,综合考虑了跨异构子网端到端传输性能最优化问题,通过层次分析法建立了跨异构子网联合资源调度模型。在此模型基础上,求解了各方案的灰度关联系数,得出了跨异构子网无线资源调度优化算法(AHP-WRA)。对AHP-WRA算法、随机接入(RA)算法和高带宽优先(HBA)算法进行了对比仿真,仿真结果表明,在系统有效吞吐量方面AHP-WRA算法明显优于其他两种算法。     

增强超宽带无线网络QoS的调度算法

基于对UWB网络中已有调度算法性能的分析,提出了一种用于增强UWB无线网络QoS的调度算法。该算法采用跨层设计的思想,能根据无线物理层信道状态和应用层业务传输速率的变化进行动态带宽分配,分配过程主要采用带宽借贷的思想,即在具有不同优先级的业务流之间进行带宽调度,以尽最大可能满足具有不同优先级的业务流QoS要求。仿真结果表明,该算法能有效地增强网络的QoS,提高整个网络的性能。     

视频点播系统中基于流行度的MBGC策略

视频节目的调度策略是视频点播系统中有效使用存储资源和网络资源的关键技术,优化的节目调度和管理可以极大的提高视频服务器的性能。根据流行度来划分视频节目的优先级,提出了一种视频节目调度算法——可移动边界保护信道法(MBGC),并设计了一个二维的Markov链对算法的性能进行了理论上的分析,最后的数值分析结果表明,提出的算法提高了系统的性能。     

CAN型网络化控制系统的混合带宽优化

A hybrid bandwidth scheduling scheme is proposed to improve the quality of service and the bandwidth utilization for the CAN-based networked control systems. It combines rate monotonic and improved round-robin scheme for both the real-time and non-real-time data. Moreover, considering the constraints of control performance and network schedulability, a heuristic branch and bound genetic algorithm (GA) algorithm is presented for the control data to minimize their bandwidth occupancy and the jitter caused by improper scheduling. The residual bandwidth is allocated to non-real-time data by the proposed scale round-robin scheme such that their network loads are balanced.     

一种基于IEEE 802.16j网络的带宽调度方案*

针对IEEE 802.16j网络,提出了一种上行业务的动态联合带宽资源调度方案。根据该网络系统树状拓扑结构,在基站BS和中继站RS间采用分级分布式资源调度体制,从而既保障了业务的带宽需求,又提升了上行带宽利用率,同时还提出了针对不同类型业务采用不同的调度算法,改善了调度的公平合理性。仿真结果表明,提出的动态联合调度方案相比严格优先级调度更具灵活性,能够在兼顾用户速率公平的条件下有效地保证各种服务的QoS要求,同时也可获得较高的带宽资源利用率。     

Feedback scheduling of priority-driven control networks

With traditional open-loop scheduling of network resources, the quality-of-control (QoC) of networked control systems (NCSs) may degrade significantly in the presence of limited bandwidth and variable workload. The goal of this work is to maximize the overall QoC of NCSs through dynamically allocating available network bandwidth. Based on codesign of control and scheduling, an integrated feedback scheduler is developed to enable flexible QoC management in dynamic environments. It encompasses a cascaded feedback scheduling module for sampling period adjustment and a direct feedback scheduling module for priority modification. The inherent characteristics of priority-driven control networks make it feasible to implement the proposed feedback scheduler in real-world systems. Extensive simulations show that the proposed approach leads to significant QoC improvement over the traditional open-loop scheduling scheme under both underloaded and overloaded network conditions.     

一种输入排队交换结构的自适应包切分策略

针对传统的输入排队交换结构的数据包切分策略带宽利用率低、灵活性差等缺点,提出一种自适应包切分策略。新策略利用集中式调度的同步特性,在调度过程中通过输入端的队列状态来确定切分单元的大小,并动态调整算法匹配时间,有效地减少了填充字节和系统所需加速比。仿真分析表明,与现有的包切分策略相比,采用自适应策略的交换结构更能适应实际网络环境,且具有良好的时延性能。     

视频服务器中多网络I/O的调度与接纳控制

在视频服务器中,由于网络I/O带宽比磁盘I/O带宽相对丰富而未得到研究者的重视,但当服务达到一定的规模、网络输出成为瓶颈时,在多网络I/O情况下,网络输出的量化计算则不可避免.着重探讨了视频服务器在多网络I/O并行输出的情况下,如何进行最大输出调度的问题,给出了3个调度算法及相应的接纳计算公式,特别是一个带缓冲的优化调度模型.实验结果显示,调度模型及规划性能是优越而有效的.该项工作对视频服务器的调度设计、资源的有效配置具有指导作用.     

Hybrid Scheduling and Quantized Output Feedback Control for Networked Control Systems

A novel co-design scheme of hybrid scheduling strategy, adaptive logarithmic quantizer and dynamic robust H-infinity output feedback controller for a class of networked control system (NCS)with communication constraints and time delay is proposed. The hybrid scheduling scheme integrates dead zone scheduling and Try Once Discard (TOD) scheduling so as to get the stronger adaptability and flexibility than the single scheduling. In this scheme, dead zone scheduling which updates the threshold according to mode-dependent control strategy is used for single node of NCS to reduce the network bandwidth utilization while TOD scheduling is used for the whole node of NCS in order to meet the requirements of communication constraints and guarantee the overall system performance.We develop the integrated design for the hybrid scheduling strategy, adaptive quantizer and dynamic robust output feedback controller to maintain asymptotic stability of the closed-loop NCS by using the multiple-Lyapunov function and switched system theory. The proposed method can improve the the quality of service (QoS) meanwhile ensure the quality of control (QoC) of overall systems, which make a better trade-off between network utilization and control performance. An simulation example demonstrates the efficiency of the proposed method.     

Structural Properties,LQG Control and Scheduling of a Networked Control System with Bandwidth Limitations and Transmission Delays

The problem of simultaneous LQG control and scheduling of a Networked Control System (NCS) with constant network induced delays at input and output and bandwidth limitations is investigated. Delays are considered at plant as well as controller side. Sufficient conditions for controllability, stabilizability, reconstructibility and detectability of the underlying networked control system are drawn. The proposed conditions extend previous works on structural properties of NCS by capturing both plant and controller side delays together with bandwidth limitations. A framework for computing the optimal LQG controller for the NCS with a fixed scheduling is provided. The proposed modeling approach facilitates use of LQG as well as other control methods for NCSs with delays and bandwidth limitations. In order to optimize performance, a semi-online scheduling procedure is proposed based on an offline look up table. The look up table assigns an optimal schedule with associated optimal LQG controller to initial conditions. The proposed scheme improves previous results by online deployment of schedule and LQG control with stability guarantees and very low computational overhead. A simulation example with communication delays, packet losses and bandwidth limitations in both sensor and actuator sides is included. Static optimal periodic communication sequence, Optimal Pointer Placement (OPP) approach proposed in previous works, a random access scheduling method representing contention based access policies and the proposed method are simulated and compared.      

Distributed Collaboration for Enhanced Sender-Driven Video Streaming

We propose a sender-driven system for adaptive streaming from multiple servers to a single receiver over separate network paths. The servers employ information in receiver feedbacks to estimate the available bandwidth on the paths and then compute appropriate transmission schedules for streaming media packets to the receiver based on the bandwidth estimates. An optimization framework is proposed that enables the senders to compute their transmission schedules in a distributed way, and yet to dynamically coordinate them over time such that the resulting video quality at the receiver is maximized. To reduce the computational complexity of the optimization framework an alternative technique based on packet classification is proposed. The substantial reduction in online complexity due to the resulting packet partitioning makes the technique suitable for practical implementations of adaptive and efficient distributed streaming systems. Simulations with Internet network traces demonstrate that the proposed solution adapts effectively to bandwidth variations and packet loss. They show that the proposed streaming framework provides superior performance over a conventional distortion-agnostic scheme that performs proportional packet scheduling on the network paths according to their respective bandwidth values.     

Bandwidth‐aware divisible task scheduling for cloud computing

Task scheduling is a fundamental issue in achieving high efficiency in cloud computing. However, it is a big challenge for efficient scheduling algorithm design and implementation (as general scheduling problem is NP‐complete). Most existing task‐scheduling methods of cloud computing only consider task resource requirements for CPU and memory, without considering bandwidth requirements. In order to obtain better performance, in this paper, we propose a bandwidth‐aware algorithm for divisible task scheduling in cloud‐computing environments. A nonlinear programming model for the divisible task‐scheduling problem under the bounded multi‐port model is presented. By solving this model, the optimized allocation scheme that determines proper number of tasks assigned to each virtual resource node is obtained. On the basis of the optimized allocation scheme, a heuristic algorithm for divisible load scheduling, called bandwidth‐aware task‐scheduling (BATS) algorithm, is proposed. The performance of algorithm is evaluated using CloudSim toolkit. Experimental result shows that, compared with the fair‐based task‐scheduling algorithm, the bandwidth‐only task‐scheduling algorithm, and the computation‐only task‐scheduling algorithm, the proposed algorithm (BATS) has better performance. Copyright © 2012 John Wiley & Sons, Ltd.