具有最低竞争吞吐率保证的准入控制算法

研究了IEEE 802.11 PCF(point coordination function)机制下集成实时业务和非实时业务的性能,提出了一种新的实时业务准入控制算法.该算法根据网络中的非实时业务负载情况动态计算准入阈值,并对准入的实时业务结点按服务指标进行轮询,从而在对实时业务提供参数化QoS(quality of service)的同时,使非实时业务吞吐率保持在可接受的水平上.仿真实验验证了算法的有效性.     

支持VoWLAN的PCF轮询调度算法研究

就802.11 WLAN中MAC层点协调功能（PCF）状态下点协调器（PC）对各个站点分配媒体访问权的轮询机制进行分析并加以改进,通过引入不同优先级的业务区分机制,提出一种新的轮询调度算法,从而提高站点数据接入服务的性能,以满足VoIP over WLAN应用的QoS需求。     

802.11e无线局域网QoS技术研究

本文分析了IEEE 802.11中DCF、PCF和IEEE 802.11e中的EDCF、HCF四种接入机制.研究了这四种机制对实时业务的QoS支持能力.通过NS-2软件仿真得出,相比于802.11中的DCF、PCF,802.11e中的EDCF、HCF机制提高了实时业务的QoS.对当前WLAN网络中实时业务的传输有着重要的指导意义.     

无线局域网中动态优先级轮询控制系统分析

论文根据IEEE802.11PCF协议轮询机制的实时特性,以基本业务群(BSS)内站点(STA)的分组数为基础,提出了一种基于优先级的动态轮询协议。阐述了该协议的基本结构以及实现算法,并对协议性能进行分析。同时也给出了计算机仿真结果,实现了对原有轮询机制性能的改善。     

802.11e无线局域网QoS技术研究

本文分析了IEEE802.11中DCF、PCF和IEEE802.11e中的EDCF、HCF四种接入机制。研究了这四种机制对实时业务的QoS支持能力。通过NS-2软件仿真得出,相比于802.11中的DCF、PCF,802.11e中的EDCF、HCF机制提高了实时业务的QoS。对当前WLAN网络中实时业务的传输有着重要的指导意义。     

无线局域网中PCF机制的实时性能研究与改进

针对MAC层公平性问题,本文对原有DCF机制进行了改进,根据节点所处的信道状态和其转发数据比例,动态调整竞争窗口大小,进行自适应二进制指数退避。就点协调功能(PCF)状态下点协调器(PC)对各个联入PC的站点分配媒体访问权的轮询机制进行分析并加以改进,提出一种令牌缓冲器的方法,仿真结果表明,改进PCF和DCF机制与IEEE802.11协议采用的退避算法相比,在信道公平性方面有较好的改善,并且具有较高的实时性。     

蓝牙系统调度策略的研究

Round Robin策略(轮询调度策略)是蓝牙系统调度的基本策略，但它存在效率低下的特点。本文针对蓝牙系统调度的特点提出一种优先级调度策略的实现方案，并建立相应的排队论，对其进行性能评价，从而得到了比Round Robin策略更好的系统性能。     

一种基于双令牌的蓝牙调度算法

调度算法是短距离无线通信技术的主要问题。蓝牙网络中使用的Round Robin (RR)轮询调度算法严重影响了系统的性能，本文针对这个问题提出了一种改进的蓝牙调度算法——双令牌随机(DTPR)轮询算法．此算法有两个重要特点：一是访问采用随机次序解决从设备之间的不公平性；二是采用优先级调度策略，对拥有令牌的主从设备对进行调度，缩短了轮询周期。并对本文提出的算法与现已提出的算法进行了仿真实验，结果表明，本文提出的算法在系统的吞吐量、传输时延和公平性方面都优于现有的其它算法。     

Ad hoc网络中基于TDMA的定向发送和接收算法

近期研究结果表明利用有向天线实现定向发送和定向接收比用全向方式能显著提高系统吞吐量.为了支持多媒体和实时业务,在Ad hoc网络中提供服务质量(QoS)是一个关键部分.提出了一种利用有向天线且提供QoS支持适用于Ad hoc网络的分布式媒体接入控制(MAC)算法.仿真结果表明该算法与IEEE 802.11相比提高了系统吞吐量并降低了端-端延迟.     

自适应IEEE802．11PCF调度算法

本文在研究现有无线局域网IEEE802．11 PCF（Point Coordination Function）调度算法基础上，提出一个自适应PCF算法的解决方案。该算法通过使用队列调度来实现CFP（Contention Free Period）阶段PC和站点之间的消息服务，站点之间的服务顺序可以根据实时需求动态改变；对来自站点大量高速率发送的数据，调度器采用队列缓冲区尾部丢弃策略来缓解网络拥塞。通过对比定性的分析了此算法与单轮询算法在CFP帧传输的性能差异，得到在系统吞吐率以及平均包延迟上本文提出的算法能提供更好的QoS。     

基于公平服务多维加权轮询调度的IPTV组播流量控制策略

根据大规模接入汇聚路由器（ACR)的总体技术规范,IPTV组播复制在ACR的以太网分合路器（EMD)中进行,而IPTV组播业务的增长会对其他业务造成冲击,因此需要对IPTV组播流量进行控制,以保证其他业务的带宽分配,针对IPTV流量控制中的关键环节──队列调度,提出了一种公平服务多维轮询调度策略(FSMWRR),性能仿真的结果表明该调度策略能够满足IPTV业务的低时延、时延抖动的需求,同时保证各个业务带宽分配的公平性。     

Power-saving scheduling with a QoS guarantee in a mobile WiMAX system

This paper presents a power-saving scheduling scheme to improve energy efficiency and guarantee Quality of Service (QoS) in Mobile Worldwide Interoperability for Microwave Access (WiMAX), i.e. IEEE 802.16e. Due to the popularization of multimedia services such as Voice over IP (VoIP) and MPEG video, different types of QoS coexist in one mobile subscriber station (MSS). Many previous studies have considered the QoS issue. Unfortunately, they only considered the delay in QoS. In this work, we consider that delay and jitter types of QoS should be scheduled at the same time and integrate the sleep duration in one MSS. The packets would be scheduled successively to reduce the number of status transitions under the QoS requirements of delay and jitter. The proposed approach not only minimizes power consumption of the MSS, but also guarantees both the delay and jitter QoS of real-time connections.     

An Approach Towards Development of a New Cloudlet Allocation Policy with Dynamic Time Quantum

Cloud computing is one of the most emerging technologies which has created a revolution in the High performance Computing (HPC) domain. The term Quality of Service (QoS) plays a vital role in the formation of more flexible integration of various technologies. The Waiting Time (WT), Turnaround Time (TAT), Context Switching (CS) and Makespan (MS) are the primary parameter that has great impact on the scheduling of cloudlets. The Proposed algorithm has improved the resource utilization system of the existing Round Robin Algorithm (RRA) and Improved Round Robin Cloudlet Scheduling Algorithm (IRRCSA) by introducing the concept of dynamically calculated Time Quantum (TQ) for each virtual machine (VM) according to the allocated cloudlets. This new approach in cloudlet scheduling drastically reduced average WT, average TAT and Number of CS of the VMs, which further enhanced the capability of cloud service providers (CSPs) to provide better QoS.     

IEEE802.16中基于自适应信道预留的呼叫接入策略

呼叫接入控制（CAC）在宽带无线接入（BWA）服务质量（QoS）中起着非常重要的作用。对无线城域网中IEEE802.16复杂的QoS定义,该文提出了一种在IEEE802.16中基于自适应资源预留的呼叫接入控制策略（AR-CAC）。该策略根据UGS负载和信道利用率为其自适应预留信道,同时考虑了IEEE802.16业务的带宽特性。仿真结果表明,该策略在硬切换呼叫切换失败概率不变的情况下降低了高优先级服务的呼叫阻塞率,同时增大了系统的吞吐量。     

LGRR: A new packet scheduling algorithm for differentiated services packet-switched networks

Since Quality of Service (QoS) support is a mandatory requirement in the next-generation networking, each router in a packet-switched network must provide a better service to higher-priority packets under any situation such as congestion. We propose in this paper the loan-grant based Round Robin (LGRR) packet scheduler for use in each output port of a router in a DiffServ network. LGRR is a frame-based scheduler to pass traffic streams according to their class types and to their immediate upstream source routers. It uses a loan-grant scheme so that a higher priority traffic stream can be processed quickly by requesting a bandwidth loan from the scheduler. To control the amount of transmitted bits from each stream and to prevent malicious abuse, the bandwidth loan must be paid back from the quantum values acquired in future. LGRR gives a fair opportunity to different traffic streams to access to the network bandwidth. It performs better than MDRR+, MDRR++, and OCGRR in handling traffic under both normal and bursty traffic, but it also gives a better loss and delay performance to the higher-priority traffic when traffic load is very high.     

WLAN中基于EDCA机制的接纳控制研究

分析IEEE802.11e的服务质量（QoS）调度机制和EDCA访问机制,基于保证通信服务质量、改良EDCA参数,适合分布式的ad hoc网络的运用,提出了一种接纳控制方案和EDCA参数调节改良机制,有效提高了媒体接入控制。     

基于数据包重传的802.11 DCF区分服务机制

针对IEEE 802.11 DCF不能为实时业务提供服务质量（QoS）保证,提出了一种基于数据包重传的区分服务机制。该机制通过对不同优先级的数据流采用不同的重传机制和重传次数,实现饱和吞吐量、饱和时延和分组丢弃概率的相对区分。然后采用二维Markov Chain模型对该机制进行数学分析与评价。数学分析表明,该机制能够有效支持区分服务,并且能够显著提高系统饱和吞吐量,获得更好的性能。     

Adaptive unequal protection for wireless video transmission over IEEE 802.11e networks

Packet loss of video streams cannot be avoided at wireless links for limited wireless bandwidth and frequently changed environments. To provide differentiated Quality of Service (QoS) guarantees between multimedia and data services, IEEE 802.11e was proposed. However, its performance and flexibility need to be further improved. In this paper, after a survey on various modifications of IEEE 802.11e, we formulate the problem of video transmission over IEEE 802.11e networks to help scheme design and performance analysis. Then accompanied with in-depth analysis, an adaptive unequal protection schema is proposed, which is composed of three mechanisms: (1) Insert each video packet into the access category (AC) with the minimum relative queuing delay; (2) Assign each packet dynamically to a proper AC based on several parameters to guarantee the transmission of high priority frames; (3) Apply fuzzy logic controllers to adjust parameters so as to reply quickly to the variation of video data rate, coding structure and network load. Finally, regarding MPEG-4 codec as the example, we perform extensive evaluations and validate the effectiveness and flexibility of proposed scheme. Simulations are divided into WLAN and multihop parts, involving different video sequences and various traffic modes of data streams. Beside performance comparison between proposed scheme and other ones, influence of parameter setting and combination with routing algorithms are also evaluated.     

基于IEEE802.11 DCF的QoS机制综述

分布式协调功能（DCF）采用有冲突避免的载波侦听多路访问（CSMA/CA,Carrier Sense Multiple Access with Collision Avoidance）方式访问共享无线媒体,是IEEE802.11媒体访问控制协议的基础。然而,在活动节点数目较大的环境下,这种机制容易造成性能恶化,且难以提供实时业务的服务质量（QoS）保证。概述了IEEE802.11的DCF机制及其性能分析方法,重点剖析了当前基于DCF的各种QoS机制,讨论了它们各自的优缺点,最后得出了优化DCF的一些有益的结论。     

Design and analysis of a frame-oriented dynamic bandwidth allocation scheme for triple-play services over EPONs

Ethernet Passive Optical Networks (EPONs) are regarded as an important technology for current access networks. However, EPONs perform poorly in differentiated service environments, and may therefore fail to meet the Quality of Service (QoS) demands of emerging triple-play services (i.e. Voice over IP, video and BE traffic). Accordingly, the present study proposes a novel Dynamic Bandwidth Allocation (DBA) scheme, designated as Frame-Oriented Interleaved Polling with Adaptive Cycle Time (FIPACT), to improve the differentiated QoS capability of EPON networks. In the proposed scheme, the Optical Line Terminal (OLT) divides the time domain of the upstream network bandwidth into a contiguous series of fixed-length frames. Within each frame, each Optical Network Unit (ONU) is guaranteed sufficient network resources to transmit a specific quota of each triple-play service. In this manner, the proposed DBA scheme can satisfy the differentiated QoS requirements of triple-play services. Therefore, based on the M/G/1 queueing analysis framework of multiuser cyclic polling systems, this study develops an analytical framework to derive the closed-form expressions for FIPACT mean packet delay. The simulation results validate the analytical results and confirm the efficiency and effectiveness of the proposed DBA scheme.