基于Fibonacci的动态带宽分配算法

针对WiMAX系统中混合业务的特点,提出一种基于Fibonacci的动态带宽分配算法。介绍Fibonacci数列以及带宽调度的体系结构,对于实时轮询业务,在达到其能容忍的最大时延之前完成带宽分配。实验结果表明,与亏空公平优先队列算法相比,该算法能满足不同类型业务的QoS需求,提高系统吞吐量,且具有较好的服务公平性。     

改进的WiMAX上行链路调度机制

基于IEEE 802.16e协议的实时业务调度机制,以及对VoIP业务特性的分析,提出了一种改进的上行链路调度机制,该调度机制自适应地调整数据带宽分配周期。从理论上分析了所提出的调度机制和已有调度机制的VoIP用户容量。系统仿真结果表明,在保证系统容量的前提下,所提出的调度机制可以有效地降低用户的上行时延,从而提高了服务质量。     

基于WiMAX的实时业务带宽优化调度策略

WiMAX是一项无线城域网(WMAN)技术,支持实时与非实时等多种业务,SS可以向BS动态申请所需求的带宽,由IEEE 802.16协议定义.但协议中没有具体定义实时服务QoS所需要的带宽调度策略.因此,如何高效地分配使用带宽,成为一个亟需解决的问题.本文提出一种自适应的实时轮询业务带宽分配策略,SS依据当前带宽需求和以往的实际分配带宽,提前预测实时业务数据包所需求的确切带宽.文中给出了数学分析模型和仿真.仿真结果表明,与传统的带宽分配机制和其他自适应算法相比,该自适应的带宽分配算法能更好地改善系统性能,提高吞吐量,减少时延和减少缓冲区需求.     

HFC接入网MAC层QoS系统架构研究与实现

针对HFC(Hybrid Fiber-Coax)接入网络服务质量保证问题,通过对DOCSIS(Data-over-Cable Service Interface Specifi-cations)QoS(Quality of Service)标准进行深入研究,采用多种QoS技术并对其进行有针对性的改进从时延、带宽等方面保证了不同调度业务的服务质量,从而给出了一种适用于HFC网络接入设备的QoS系统解决方案.网络仿真结果显示采用该QoS系统架构提高了信道带宽利用率,保证了高优先级调度业务对带宽、时延等要求,尽量级联的级联策略使上行带宽利用率提高了大约25%.此外,该QoS系统架构已经成功应用于符合EuroDOCSIS1.1规范的支持双向有线电视点播平台中,通过了功能验证并表现出良好的稳定性.     

一种适用于宽带无线多媒体网络的上行带宽分配方案

提出了一种适用于宽带无线多媒体网络的上行无线带宽分配方案。该方案将业务数据分为3种类型,即实时恒定速率业务、恒定变速率业务、非实时业务,针对不同业务对时延和带宽的不同需求,采取不同的方法获取上行带宽,较好地解决了多业务并发时的上行带宽分配问题,较传统技术提高了带宽利用率,减少了协议开销和传输时延。在详细描述算法的基础上,建立了对应的仿真系统对算法进行了验证。     

IEEE 802.11e协议HCCA机制下的QoS研究

分析了IEEE 802.11e协议HCCA信道接入机制下的简单带宽调度算法对多媒体业务的QoS支持情况,指出其不足并在其基础上进行了改进,提出了一种基于业务等级的带宽调度算法E-HCCA（Enhanced HCCA）。E-HCCA对不同优先等级业务的数据在带宽分配上采用不同的策略,在优先保证各个节点CBR业务的基础上,根据节点的VBR流量动态平均分配剩余带宽。相比较简单调度算法,E-HCCA算法更好地支持了多用户下的语音业务流和视频业务流,降低了分组时延,增加了系统吞吐率。     

一种用于升空平台MAC层的调度架构

为满足升空平台的协议和不同业务流的属性需求,提出了一种完整的可以满足介质访问控制层服务质量和动态带宽分配的有效的调度方案,该调度方案不仅包括移动中心站对移动站的带宽分配,还包括移动站内上行业务的二级带宽分配架构。在仿真中通过对时隙发送特性、不同业务的延时特性,以及同种业务下不同算法的时延比较,验证了该调度方案的可行性。     

一种以太网无源光网络（EPON）动态带宽分配算法

对EPON系统的上行信道复用技术进行了深入的研究。在EPON系统上行信道复用技术中,带宽分配算法是一个热点和难点。文章基于DifrerServ模型探讨了一种支持多业务的、保证QoS的混合动态带宽分配算法（HBA）,并与静态、动态带宽分配算法进行了仿真比较。结果表明HBA算法在时延、时延抖动和信道利用率等方面优于其它算法。     

WLAN与EPON融合接入网上行带宽分配算法

为了提高带宽的利用率,提出一种WLAN与EPON融合接入网上行带宽分配算法。该算法将无线终端接入的业务分为不同的服务等级,以实现不同业务Qo S保证。首先,ONU-AP给各个无线终端STA分配带宽,采用IEEE 802.11E协议的简单调度算法给语音业务和一般数据业务分配带宽,利用视频流的平均速率估算视频业务的传输带宽。其次,光线路终端OLT给各个ONU-AP分配带宽,OLT根据语音业务速率和当前视频业务流量分别估算语音、视频业务在下一个轮询周期的带宽,并将剩余带宽在重负载终端中二次分配,最后给一般数据业务分配带宽。通过仿真实验,结果表明:与传统算法相比,该算法的网络时延和丢包率明显降低,实现了带宽资源的合理分配。     

一种分层多描述编码的动态带宽分配策略

针对无线流媒体业务带宽资源有限的特点,提出一种基于分层多描述编码的动态带宽分配策略LMDBA.该策略利用了分层多描述编码的特性实现动态带宽分配,并采用QoS升降级策略,在保证用户QoS的前提下,尽可能地降低系统阻塞,提高系统带宽资源利用率.并对QoS升降级策略进行了公平性分析.仿真实验结果表明,在提供一定用户QoS保证下,提出的新策略比传统固定带宽分配策略在带宽资源利用率和系统阻塞上有显著的改善.     

基于WiMAX的VoIP的QoS改进

为了提高无线资源的利用率,使WiMAx系统更好地支持语音业务,基于IEEE802．16e协议的QoS调度体系和已有的信息流优先级（Traffic Priority）,引入新的信息流优先级乘数（Tra所cPriority Multiplier）概念,提出使用高优先级的BE服务流承载SIP信令,以取代目前普遍使用nrtPS承载SIP信令的做法。通过对优先级乘数的不同设置,可以使WiMAX运营商更加灵活地分配有限的无线资源,从而提供更好的网络和语音服务。     

Design and simulation of an efficient real-time traffic schedulerwith jitter and delay guarantees

In this paper, we propose a framework for real-time multimedia transmission in asynchronous transfer mode (ATM) networks using an efficient traffic scheduling scheme called multilayer gated frame queueing (MGFQ). MGFQ employs only one set of FIFO queues to provide a wide range of QoS for real-time applications. We also propose special cell formats for real-time multimedia transport and a hybrid design to allow MGFQ to combine its scheduling scheme with Age Priority Packet Discarding scheme. For this hybrid design, the cell level performance as well as the packet level QoS can be improved at the same time, Simulation results show that this hybrid design will be useful for packetized voice and progressive layer-compressed video transmission across the backbone networks. With the presented framework and the MGFQ algorithm, real-time multimedia traffic streams can be much better supported in terms of cell/packet delay and jitter     

A cross-layer elastic CAC and holistic opportunistic scheduling for QoS support in WiMAX

QoS provisioning is an important issue in the deployment of broadband wireless access networks with real-time and non-real-time traffic integration. An opportunistic MAC (OMAC) combines cross-layer design features with opportunistic scheduling scheme to achieve high system utilization while providing QoS support to various applications. A single scheduling algorithm cannot guarantee all the QoS requirements of traffics without the support of a suitable CAC and vice versa. In this paper, we propose a cross-layer MAC scheduling framework and a corresponding opportunistic scheduling algorithm in tandem with the CAC algorithm to support QoS in WiMAX point-to-multipoint (PMP) networks. Extensive experimental simulations have been carried out to evaluate the performance of our proposal. The simulation results show that our proposed solution can improve the performance of WiMAX networks in terms of packet delay, packet loss rate and throughput. The proposed CAC scheme can guarantee the admitted connections to meet their QoS requirements.     

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。     

一种针对混合的实时/非实时业务的无线调度算法

提出一种针对混合的实时/非实时业务的无线调度算法TF-RNS。该算法的目标是在实时和非实时用户提供公平服务时间的基础上,提高用户的服务质量。由于实时和非实时用户具有不同的服务质量要求,TF-RNS采用独立、分级的调度结构：在第一级调度过程中,分别使用M-LWDF和PF算法对实时和非实时用户进行独立的调度判决;而在第二级调度过程中,使用SFQ-CS公平调度算法保证调度的公平性,同时兼顾了用户的信道条件。仿真结果表明,与现有的M-LWDF和DS-PF算法相比,TF-RNS算法能够使实时和非实时用户获得公平的服务时间,从而有效地保证了系统中所有用户的服务质量。     

一种基于WiMAX mesh网络的区分服务调度方案

IEEE 802.16支持多种不同类型的调度服务,并将服务质量支持机制引入媒体接入控制层,却没有规定相应的调度算法。在IEEE 802.16定义的mesh模式下,针对不同类型服务,提出了一种区分服务的调度方案,该方案采用集中式和分布式混合调度。仿真结果表明:该方案下系统平均时延和用户满意度均有所改善。     

Upper-level scheduling supporting multimedia traffic in cellular data networks

Wireless data networks such as cdma2000 1x EV-DO and UMTS HSDPA use downlink scheduling that exploits channel fading to increase the system throughput. As future wireless networks will eventually support multimedia and data traffic together, we need a proper criterion for scheduling that can count various service requirements such as delay and packet loss. Although some previous approaches proposed opportunistic schedulers at the lower layer, it has not been investigated well whether they are able to meet explicit QoS defined at the upper layer. Hence, in this paper, we develop a hierarchical scheduling model that considers QoS provisioning and the time-varying channel feature separately. We focus on the upper-level QoS scheduling that supports various traffic classes in a unified manner. Supposing that a user gets some satisfaction or utility when served, we introduce a novel concept of opportunity cost, which is defined as the maximum utility loss among users incurred by serving a particular user at the current turn. We obtain each user’s net profit by subtracting the opportunity cost from its expected utility, and then select a user with the maximum profit for service. Simulation results reveal that our scheme supports various QoS classes well that are represented by delay and packet loss under various traffic loadings.     

Link-level traffic scheduling for providing predictive QoS in wireless multimedia networks

A set of centralized burst-level cell scheduling schemes, namely, First Come First Served with Frame Reservation (FCFS-FR), FCFR-FR+, Earliest Deadline First with Frame Reservation (EDF-FR), EDF-FR+, and Multitraffic Dynamic Reservation (MTDR), are investigated for transmission of multiservice traffic over time division multiple access (TDMA)/time division duplex (TDD) channels in wireless ATM (WATM) networks. In these schemes, the number of time slots allocated to a virtual circuit (VC) during a frame-time is changed dynamically depending on the traffic type, system traffic load, the time of arrival (TOA)/time of expiry (TOE) value of the data burst and data burst length. The performances of these schemes are evaluated by computer simulation for realistic voice, video and data traffic models and their quality-of-service (QoS) requirements in a wireless mobile multimedia network. Both the error-free and the correlated fading channel conditions are considered. Simulation results show that the EDF-FR+ and MTDR schemes outperform the other schemes and can provide high channel utilization with predictive QoS guarantee in a multiservice traffic environment even in the presence of bursty channel errors. The EDF-FR+ scheme is found to provide better cell multiplexing performance than the MTDR scheme, Such a scheme would be easy to implement and would also result in a power conservative TDMA/TDD medium access control (MAC) protocol for broadband wireless access. Burst-level cell scheduling schemes such as EDF-FR+ can be easily adapted as MAC protocols in the emerging differentiated services (DS) enhanced wireless Internet protocol (IP) networks.     

Above packet level admission control and bandwidth allocation for IEEE 802.16 wireless MAN

IEEE 802.16 wireless Metropolitan Area Network (MAN) is expected to revolutionize the broadband wireless access technology. Efficient resource management is essential in providing scalability in such large IEEE 802.16-based wireless network and Quality of Service (QoS) for multimedia applications (VoIP, MPEG, FTP, WWW) is usually achieved by appropriate classification of scheduling services and grant/request mechanism. In this paper, we firstly discuss the QoS issue in IEEE 802.16 wireless MANs and propose a dynamic admission control scheme for scheduling services defined in the 802.16 specification. The proposed scheme provides the highest priority for Unsolicited Grant Service (UGS) connections and maximizes the bandwidth utilization by employing bandwidth borrowing and degradation. We develop an approximate analytical model to evaluate the system performance by assuming that the traffic processes of all scheduling services are Poisson processes. In fact, the self-similarity of non-voice traffic makes its traffic process far from Poisson process and should be modeled by Poisson Pareto Burst Process (PPBP). Therefore, in the later part of the paper, we analyze upper bound blocking probabilities of all scheduling services above the packet level using PPBP model for fractal traffic and Gaussian model for aggregated traffic in large wireless network as well as using the Chernoff bound method. Based on the analytical results, we give another admission control and bandwidth allocation mechanism above the packet level so as to minimize the blocking probability of each type of service in IEEE 802.16 wireless MAN. Analytical and simulation results are obtained and compared to demonstrate the effectiveness of proposed schemes and validate our analytical models.     

FLEXIBLE FUZZY PRIORITY SCHEDULING OF THE CAN BUS

With the increasing complexity of distributed real‐time systems, the need for improved CAN bus performance is continually increasing. Normally, a scheduling scheme with static‐priority has low network schedulability/utilization; while using dynamic priority will improve the QoS of the network at the cost of a narrow service range or a high overhead, compared with the fixed priority scheduling schemes. Actually, because of the fluctuation of network traffic, these priority policies may not guarantee flexibility for different kinds of messages. Based on the broadcast nature of the CAN bus, a closed‐loop fuzzy scheduling scheme is proposed in this paper. Compared with the dynamic priority schemes, this fuzzy scheduling scheme uses fewer bits to encode fewer priority levels, which widens the service range of the network without increasing overhead. Based on game theory, a fuzzy parameter updating algorithm for the fuzzy scheme is developed to improve the adaptation of the scheme, which guarantees the required QoS of the network even with traffic fluctuation. Simulation results well demonstrate the abilities of the fuzzy scheme to guarantee high schedulability for real‐time messages, as well as the fairness and the same QoS for non‐real‐time messages in networks.