DTN中基于服务等级的Push-Pull拥塞控制研究*

提出了一种基于服务等级的拥塞控制机制,通过为后续高优先级业务预留缓存资源的方法来减小容迟网络(DTN)中由于保管传输协议造成节点缓存资源的耗尽而引起的网络拥塞,从而改善服务质量。仿真结果表明,该拥塞控制方法在缓解网络拥塞的同时可以有效改善高优先级业务的传输性能,但其在一定程度上牺牲了低优先级业务的服务质量。     

无线传感器网络中一种避免节点拥塞的算法

无线传感器网络节点拥塞导致节点丢弃大量的数据包,这不仅影响了网络服务质量,还浪费了节点宝贵的能量,进而缩短了网络生命周期.提出了一种避免传感器网络节点拥塞的算法.该算法包含了基于发送窗口分配的拥塞避免和基于优先级的数据包调度策略.网络节点首先根据一定策略为上一跳节点分配发送窗口来预防本地发生拥塞,获得发送窗口的上一跳节点每次选择优先级最高的数据包发送以改善网络服务质量.模拟实验表明,提出的算法具有良好的能量有效性,有效地避免了由节点缓冲区溢出造成的网络丢包,同时改善了网络传输的公平性并降低了网络的平均延迟.     

WiMAX Mesh网络中一种集中式QoS调度算法

针对WiMAX Mesh网络集中式下资源的调度和分配,分析了现有调度算法的研究进展与优缺点,结合标准对Mesh模式的QoS定义,提出了一种WiMAX Mesh网络集中式下基于分组的QoS调度算法。通过区分数据流的优先级方式对不同业务数据流进行分组,并计算组内流节点的权值,保证同种业务流间高传输要求和低传输节点的公平性。仿真结果表明,与HRF和LRC算法相比,该算法对于分类业务的时延和网络吞吐量具有明显的优势,实现了区分业务的QoS保障。     

IEEE 802.11e无线局域网中VoIP容量分析及改进

IEEE 802.11e提供了对不同的业务流进行优先级区分的机制,提高了无线局域网（WLAN）内VoIP等实时业务相对于其他业务流的优先性,从而在一定程度上保障其QoS要求,但并没有对WLAN中移动节点（MH）和接入节点（AP）进行优先级的区分,导致AP处上下行业务流量的不平衡,并造成瓶颈效应,限制了VoIP容量。针对这一问题,在对WLAN中VoIP进行容量分析的基础上,提出一种改进AP信道接入能力的策略。通过对AP中队列长度的检测来判断网络拥塞程度,从而动态调整AP的仲裁帧间间隔（AIFS）,以达到根据网络拥塞状况来动态调整AP的优先级,弱化AP的瓶颈效应对VoIP容量制约的目的。仿真结果表明,所提出的改进方案能够有效地提高WLAN中的VoIP容量。     

实时企业服务总线的研究与设计

针对现有企业服务总线在不同类型业务流竞争有限带宽资源时产生系统拥塞的问题,提出一种实时企业服务总线模型.对JBI标准进行了改进,增加了业务优先级和业务时间约束的语义,并加入流量控制和带宽分配组件.系统运行时能根据不同类型业务流带宽需求,按照业务类型优先级从高到低动态分配服务总线的业务流量带宽.仿真实验结果表明,该方法可以保证高优先级业务的带宽需求,减少因业务拥塞导致的服务质量下降,并进而提升系统整体的吞吐能力.     

基于改进Dijkstra算法的配用电通信网流量调度策略

针对配用电通信网中数据汇聚易产生拥塞的问题,提出了一种复合边权值流量调度路由算法。首先,依据跳数建立节点分层模型;然后,划分配用电业务优先级和节点拥塞等级;最后,以跳数、流量负载率和链路利用率为综合指标计算边权值,对需要流量调度的节点根据改进的Dijkstra算法进行路由选择,同时对重度拥塞节点按照配用电业务优先级进行调度。与最短路径（SPF）算法和贪婪背压算法（GBRA）相比,在数据生成率为80 kb/s时,所提算法紧急型业务丢包率分别减少了81.3%和67.7%,关键型业务丢包率分别减少了79%和63.8%。仿真结果表明,所提算法能有效缓解网络拥塞,提高网络有效吞吐量,降低网络端到端时延和高优先级业务的丢包率。     

基于效用的EPON VoD QoS组播实现机制研究

服务质量无法保证和低效益是IP网络上开展VoD业务面临的主要问题.基于组播业务的网络优先级、用户群的SLA优先级和经济优先级,提出了一个基于效用的EPON VoD组播QoS优先级(效用优先级)算法.在网络拥塞的时候,基于该效用优先级来动态调整组播组的资源分配,不但节省了带宽需求和降低包丢失率,而且可通过将网络资源汇聚到高价值的业务上,提高带宽的效益.通过对变长和无序EPON Ethernet下行帧进行基于效用的定长和有序的改进,可减少VoD业务流的包时延抖动.仿真实验结果很好地验证了该机制的优点.     

数据中心网络中基于传输速率分配算法的TCP协议

传输控制协议(Transmission Control Protocol,TCP)是数据中心网络中常用的传输协议。然而,同一个网络环境下,由于TCP协议的公平共享原则,TCP无法保障不同优先级业务的服务质量。针对该问题,提出了基于传输速率分配算法的TCP(Transmit Rate Allocation based TCP,TRA-TCP)。汇聚节点实时监测记录不同优先级业务的数据传输速率,并为不同优先级的业务流分配不同的传输速率,以保障高优先级业务的QoS。实验表明,与已有协议相比,TRA-TCP协议最高能够将高优先级业务的吞吐量提升50%,并且将高优先级业务的时延保持在0.1秒以下。     

一种基于拥塞避免的自适应退避算法的研究

本文在二进制指数退避算法基础上提出一种基于拥塞避免的自适应退避算法.该算法引入了拒绝帧NTS,使接收节点具有拒绝发送节点发送请求的能力;另外通过将接收节点的拥塞状况反馈到发送节点,使发送节点可以根据自身待发送数据流的QoS属性和接收节点的拥塞状况自适应地调整退避参数,最终实现对高优先级数据流的保护.仿真结果表明,该算法能有效地保护高优先级数据流的端到端吞吐量、减小其分组重传次数以及分组时延,从而达到提高系统性能的目的.     

一种基于动态带宽分配的企业服务总线模型

现有的企业服务总线(ESB)系统在重载时会发生业务拥塞并导致服务质量下降。针对该问题,提出一种基于动态带宽分配的ESB模型。将总线上运行的各个业务流分为3种级别的业务类型。系统在运行时按业务类型优先级为业务流量动态分配带宽,以保证高优先级业务的带宽需求,减少拥塞的发生,提高系统的吞吐能力。实验结果证明了该模型的有效性。     

无线传感器网络中一种ARMA流量预测的拥塞控制算法

在无线传感器网络中,由于各节点的通信能力、计算能力、存储能力等都比较有限,使其需采取有别于传统网络的拥塞控制策略.本文针对传感网络特有的多对一、多跳通信方式经常导致网络拥塞的缺陷,提出一种基于流量预测的拥塞避免算法(SCATP).该算法通过ARMA模型分析流经各节点的当前流量,预测网络下一时刻的拥塞状况,并据此进行流量分配,从而实现拥塞控制的同时保证数据的可靠传输.仿真实验表明,SCATP算法在延迟、抖动率、吞吐量和能量有效性等方面能有效改善网络的服务质量.     

Priority-based rate control for service differentiation and congestion control in wireless multimedia sensor networks

In wireless multimedia sensor networks (WMSNs) a sensor node may have different types of sensor which gather different kinds of data. To support quality of service (QoS) requirements for multimedia applications having a reliable and fair transport protocol is necessary. One of the main objectives of the transport layer in WMSNs is congestion control. We observe that the information provided may have different levels of importance and argue that sensor networks should be willing to spend more resources in disseminating packets carrying more important information. Some applications of WMSNs may need to send real time traffic toward the sink node. This real time traffic requires low latency and high reliability so that immediate remedial and defensive actions can be taken when needed. Therefore, similar to wired networks, service differentiation in wireless sensor networks is also an important issue. We present a priority-based rate control mechanism for congestion control and service differentiation in WMSNs. We distinguish high priority real time traffic from low priority non-real time traffic, and service the input traffic based on its priority. Simulation results confirm the superior performance of the proposed model with respect to delays, delay variation and loss probability.     

基于区分服务的无线多媒体传感器网络QoS路由协议*

针对无线多媒体传感器网络数据量大且不同业务传输的QoS约束不同的特点,提出了一种数据融合的区分服务的QoS路由算法（DF-DSQR）。该算法在兴趣泛洪期间建立实时（RT）和尽力而为（BE）业务两类梯度,采用优先级排队模型对两类业务的传输进行分级处理,并采用数据融合转发机制,为RT业务和BE业务提供了保证QoS的路由路径。仿真结果表明,该算法既能保证实时业务低时延的要求,又能保证尽力而为业务的QoS要求,均衡了网络能耗,延长了网络生存期。     

Differentiation, QoS guarantee, and optimization for real-time traffic over one-hop ad hoc networks

Nodes having a self-centrically broadcasting nature of communication form a wireless ad hoc network. Many issues are involved to provide quality of service (QoS) for ad hoc networks, including routing, medium access, resource reservation, mobility management, etc. Previous work mostly focuses on QoS routing with an assumption that the medium access control (MAC) layer can support QoS very well. However, contention-based MAC protocols are adopted in most ad hoc networks since there is no centralized control. QoS support in contention-based MAC layer is a very challenging issue. Carefully designed distributed medium access techniques must be used as foundations for most ad hoc networks. In this paper, we study and enhance distributed medium access techniques for real-time transmissions in the IEEE 802.11 single-hop ad hoc wireless networks. In the IEEE 802.11 MAC, error control adopts positive acknowledgement and retransmission to improve transmission reliability in the wireless medium (WM). However, for real-time multimedia traffic with sensitive delay requirements, retransmitted frames may be too late to be useful due to the fact that the delay of competing the WM is unpredictable. In this paper, we address several MAC issues and QoS issues for delay-sensitive real-time traffic. First, a priority scheme is proposed to differentiate the delay sensitive real-time traffic from the best-effort traffic. In the proposed priority scheme, retransmission is not used for the real-time traffic, and a smaller backoff window size is adopted. Second, we propose several schemes to guarantee QoS requirements. The first scheme is to guarantee frame-dropping probability for the real-time traffic. The second scheme is to guarantee throughput and delay. The last scheme is to guarantee throughput, delay, and frame-dropping probability simultaneously. Finally, we propose adaptive window backoff schemes to optimize throughput with and without QoS constraints.     

面向无线传感器网络不同业务的区分服务算法

针对无线传感器网络中不同等级业务在传输过程中对QoS的不同要求,提出了一种适合无线传感器网络中不同业务的区分服务算法——EMHNS算法。该算法根据不同等级的业务来选择合适的转发节点,从而保证实时业务传输的时延能够达到最小,而尽力而为业务传输时时延不是考虑的主要因素,在传输尽力而为业务的时候重点考虑网络能耗均衡。仿真结果表明,与定向扩散协议相比,该算法能降低实时业务的端对端延时,并使网络生存期得到提高。     

Intelligent QoS management for multimedia services support in wireless mobile ad hoc networks

In this paper, we propose a new intelligent cross-layer QoS support for wireless mobile ad hoc networks. The solution, named FuzzyQoS, exploits fuzzy logic for improving traffic regulation and the control of congestion to support both real-time multimedia (audio/video) services and non-real-time traffic services. FuzzyQoS includes three contributions: (1) a fuzzy logic approach for best-effort traffic regulation (FuzzyQoS-1), (2) a new fuzzy Petri nets technique (FuzzyQoS-2) for modeling and analyzing the QoS decision making for traffic regulation control, and (3) a fuzzy logic approach for threshold buffer management (FuzzyQoS-3). In FuzzyQoS-1, the feedback delay information received from the network is used to perform a fuzzy regulation for best-effort traffic. Using fuzzy logic, FuzzyQoS-3 uses fuzzy thresholds to adapt to the dynamic conditions. The evaluation of FuzzyQoS performances was studied under different mobility, channel, and traffic conditions. The results of simulations confirm that a cross layer design using fuzzy logic at different levels can achieve low and stable end-to-end delay, and high throughput under different network conditions. These results will benefit delay- and jitter-sensitive real-time services.     

数据收集传感器网络的负载平衡网络构建方法

传感器网络所具有的集中式数据收集、多跳数据传输、多对一流量模式这3种特征会造成漏斗效应的出现,这会导致严重的包碰撞、网络拥塞、包丢失,甚至拥塞崩溃,还会导致能量消耗的热点的出现,使某些节点甚至整个网络过早死亡.负载平衡技术能够有效缓解漏斗效应的产生.针对静态数据收集传感器网络,基于供求网络的思想,提出了一种分布式算法,将传感器节点组织成交易平衡网络,用于平衡传感器节点的负载.利用这种方法组织而成的网络结构不是一棵负载平衡树,而是一个负载平衡网络.实验结果验证了这种方法的有效性.     

基于网络节点输出速率调节的非线性拥塞控制及稳定性鲁棒性分析

该文针对计算机高速互联网中最大服务交通流即能控交通流的拥塞调节问题,提出了一种基于网络节点输出速率调节的非线性拥塞控制机制并对其进行了稳定性和鲁棒性分析。克服了传统的基于输入端控制需要信源端和传输通道多重支持的约束。在单个节点的业务流模型基础上,将信源输入视为系统的扰动,通过调节输出速率来控制节点队列稳定。运用OPNET仿真软件对其进行了不同输入和工作条件下的仿真,结果显示,在所设计的非线性模糊PID队列控制机制下,队列稳定性好且具有较好的鲁棒性和抗干扰性。     

节点传输半径对无线自组织网络容量的影响分析*

在共享无线信道的多跳无线自组织网络中,节点传输半径的大小直接影响节点的一跳吞吐量和业务流传输的中继所需跳数,从而影响网络容量。在网络业务类型一致的条件下,通过数学模型分析和仿真实验,考察了网络容量与节点传输半径、业务流传输的路径长度以及网络节点数量之间的关系,其分析结果有助于优化无线网络的组网结构。     

On the optimality of field-line routing in massively dense wireless multi-hop networks

We consider the load balancing problem in large wireless multi-hop networks by applying the continuum approximation. The task is to find routes, geometric curves, such that the maximal traffic load in the network is minimized. In finite fixed networks, multi-path routes generally yield a lower congestion and thus allow higher throughput. In contrast, we show that in dense wireless multi-hop networks, the optimal load balancing can be achieved by a destination based single-path routing referred to as field-line routing. This is because any routing can be transformed to the corresponding field-line routing with the same or better performance, by using as paths, the field lines of the so-called destination flow associated with the original routing. The concepts are illustrated with two examples. In the case of a unit disk with unit traffic, the maximal load of 0.389 of a multi-path routing system is reduced to 0.343 by using the field-line routing. Similar improvements are also demonstrated for the unit square.