WLAN与EPON融合接入方案及带宽分配机制研究

将EPON与WLAN相结合,设计了一种基于BoF的WLAN与EPON融合接入方案。探讨了系统的上行带宽分配机制,给出了ONU-AP在竞争期和非竞争期对STA的带宽分配策略。OLT采用带宽预测的方法实现了ONU-AP的带宽分配,完成了EF业务和AF业务的带宽预测。最后,给出了具体的带宽分配算法。     

WDM EPON中的动态波长带宽分配算法

基于WDM EPON系统结构和已有波长带宽分配算法(DWBA)的不足,提出了一种结合流量预测与预分配机制的动态波长带宽分配算法--DWBPA.仿真表明在不同网络负载情况下,该算法不仅保证了波长带宽分配的公平性,而且能够满足高优先级业务的延时要求.     

基于业务认知的多用户带宽分配方法

无线局域网的MAC协议难以兼顾多用户差别的业务需求和网络吞吐量的有效性。建立具有超帧结构的带宽分配模型和具有惩罚函数的优化目标,计算满足单用户QoS需求的最小带宽,进而提出基于业务认知的多用户带宽分配算法(TCBAA)。该算法优先满足用户QoS要求,其次最大化系统的吞吐量。理论和仿真实验显示:相比于固定分配机制和最大吞吐量分配机制,TCBAA能够在有限带宽下满足更多用户的QoS需求。     

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%。     

基于合作博弈的多虚拟机实时迁移带宽分配机制

IaaS云计算平台采用虚拟机实时迁移技术进行资源动态调度和管理。在实际应用场景下,需要并行实时迁移多个虚拟机。由于实时迁移算法本身以最大利用带宽的方式进行数据传输,存在着迁移进程间竞争带宽的问题,无法保证带宽全局最优分配,影响整体迁移的性能。提出一种基于合作博弈的多虚拟机实时迁移带宽分配机制,将带宽分配问题建模为一个纳什议价,通过求解纳什议价解得到帕累托最优的带宽分配方案,并在实际的虚拟化平台上进行了实现。实验结果表明,相比标准的并行实时迁移,所提出的带宽分配机制能够公平有效地分配带宽,提高了并行实时迁移的性能。     

基于多重分形小波GPON带宽分配算法

当前吉比特无源光网络中动态带宽分配算法主要是基于轮询机制,该算法是OLT根据各个ONU发送请求带宽信息进行动态分配带宽,但该算法不能实时获取各个ONU的请求信息.由于GPON网络业务流量具有多重分形特性,因此可以通过多重分形小波对网络流量进行预测,得到ONU实时的带宽信息.文章将预测结果应用于GPON上行信道动态带宽分配,提出一种改进动态带宽分配算法.     

ATM基于预测的动态带宽分配及仿真

研究了ATM通信网络在通信业务量控制中的带宽资源分配问题,提出了基于变遗忘因子的递推最小二乘预测的动态带宽分配决策的基本原理,建立了以实时预测值作为反馈的网络资源分配机制,并通过一个实例仿真和分析表明了这种方法的可行性。     

基于多业务预测的EPON动态带宽分配算法

针对EPON系统中上行链路的时分复用机制,提出了一种基于多业务预测的动态带宽分配算法.该算法根据各个优先级业务的实时变化,通过一定的预测机制,实现动态分配带宽.相对其它算法,该算法能在保障高优先级业务优先的同时,降低数据时延.     

带宽自适应技术在iTV业务保障中的应用

介绍了带宽自适应技术在iTV业务保障中的应用过程,探索解决电信多产品业务需求之间存在的带宽分配矛盾,从而保障电信各类产品的服务质量。     

面向业务的带宽预测及分配方法的研究

针对目前的带宽预测主要围绕聚合流量的问题,本文将IP网络承载业务分类,分析了数据、语音、视频等业务的特性及QoS需求,通过建立时延与缓存长度的映射关系,提出一种既满足业务流量的统计特性,又考虑不同业务的可容忍时延及丢失率的带宽预测及分配方法.这种预测及分配方法区分对待网络承载的业务,适用于细粒度的网络资源管理和流量控制.     

Performance of packet voice transmission using IEEE 802.16 protocol

The IEEE 802.16 standard defines three types of scheduling services for supporting real-time traffic, unsolicited grant service (UGS), real-time polling service (rtPS), and extended real-time polling service (ertPS). In the UGS service, the base station (BS) offers a fixed amount of bandwidth to a subscriber station (SS) periodically, and the SS does not have to make any explicit bandwidth requests. The bandwidth allocation in the rtPS service is updated periodically in the way that the BS periodically polls the SS, which makes a bandwidth request at the specified uplink time slots and receives a bandwidth grant in the following downlink subframe. In the ertPS service, the BS keeps offering the same amount of bandwidth to the SS unless explicitly requested by the SS. The SS makes a bandwidth request only if its required transmission rate changes. In this article we study the performance of voice packet transmissions and BS resource utilization using the three types of scheduling services in IEEE 802.16-based backhaul networks, where each SS forwards packets for a number of voice connections. Our results demonstrate that while the UGS service achieves the best latency performance, the rtPS service can more efficiently utilize the BS resource and flexibly trade-off between packet transmission performance and BS resource allocation efficiency; and appropriately choosing the MAC frame size is important in both the rtPS and ertPS services to reduce packet transmission delay and loss rate     

Cell Switching Versus Packet Switching in Input-Queued Switches

Input Queued (IQ) switches have been well studied in the past two decades by researchers. The main problem concerning IQ switches is scheduling the switching fabric in order to transfer packets from input ports to output ports. Scheduling is relatively easier when all packets are of the same size. However, in practice, packets are of variable length. In the current implementation of switches, variable length packets are segmented into fixed length packets—also knowns as cells—for the purpose of scheduling. However, such cell-based switching comes with some significant disadvantages: (a) loss of bandwidth due to the existence of incomplete cells; and (b) additional overhead of segmentation of packets and re-assembly of cells. This is a strong motivation to study packet-based scheduling, i.e., scheduling the transfer of packets without segmenting them. The problem of packet scheduling was first considered by Marsan They showed that under any admissible Bernoulli IID (independent and identically distributed) arrival traffic, a simple modification of the Maximum Weight Matching (MWM) algorithm achieves 100% throughput. In this paper, we first show that no work-conserving (i.e., maximal) packet-based algorithm is stable for arbitrary admissible arrival processes. Thus, the results of Marsan are strongly dependent on the arrival distribution. Next, we propose a new class of “waiting” algorithms. We show that the “waiting”-MWM algorithm is stable for any admissible traffic using the fluid limit technique. We would like to note that the algorithms presented in this paper are distribution independent or universal. The algorithms and proof methods of this paper may be useful in the context of other scheduling problems.     

Performance Evaluation of the IEEE 802.16 MAC for QoS Support

The IEEE 802.16 is a standard for broadband wireless communication in metropolitan area networks (MAN). To meet the QoS requirements of multimedia applications, the IEEE 802.16 standard provides four different scheduling services: unsolicited grant service (UGS), real-time polling service (rtPS), non-real-time polling service (nrtPS), and Best Effort (BE). The paper is aimed at verifying, via simulation, the effectiveness of rtPS, nrtPS, and BE (but UGS) in managing traffic generated by data and multimedia sources. Performance is assessed for an IEEE 802.16 wireless system working in point-to-multipoint (PMP) mode, with frequency division duplex (FDD), and with full-duplex subscriber stations (SSs). Our results show that the performance of the system, in terms of throughput and delay, depends on several factors. These include the frame duration, the mechanisms for requesting uplink bandwidth, and the offered load partitioning, i.e., the way traffic is distributed among SSs, connections within each SS, and traffic sources within each connection. The results also highlight that the rtPS scheduling service is a very robust scheduling service for meeting the delay requirements of multimedia applications     

Efficient Traffic Scheduling for Real Time VBR MPEG Video Transmission Over DOCSIS-Based HFC Networks

Data-over-cable service interface specifications (DOCSIS), the de facto standard in the cable industry, defines a scheduling service called real-time polling service (rtPS) to provision quality of service (QoS) transmission of real-time variable bit rate (VBR) videos. However, the rtPS service intrinsically has high latency, which makes it not applicable to real-time traffic transport. In this paper, we present a novel traffic scheduling algorithm for hybrid fiber coax (HFC) networks based on DOCSIS that aims to provide QoS for real-time VBR video transmissions. The novel characteristics of this algorithm, as compared to those described in published literatures, include 1) it predicts the bandwidth requirements for future traffic using a novel traffic predictor designed to provide simple yet accurate online prediction; and 2) it takes the attributes of physical (PHY) layer, media access control (MAC) layer and application layer into consideration. In addition, the proposed traffic scheduling algorithm is completely compatible with the DOCSIS specification and does not require any protocol changes. We analyze the performance of the proposed traffic predictor and traffic scheduling algorithm using real-life MPEG video traces. Simulation results indicate that 1) the proposed traffic predictor significantly outperforms previously published techniques with respect to the prediction error and 2) Compared with several existing scheduling algorithms, the proposed traffic scheduling algorithm surpasses other mechanisms in terms of channel utilization, buffer usage, packet delay, and packet loss rate.     

一种分级WFQ的宽带无线接入系统QoS架构

文章介绍了加权公平排队(WFQ)分组调度算法和IEEE 802 16的QoS架构.在此基础上,文章结合分级WFQ分组调度算法和IEEE 802 16协议中所提供的控制机制提出了一种适合于BWA系统的QoS架构.该架构充分利用IEEE 802.16提供的控制机制,结合分级WFQ公平队列调度算法,在主动授予业务(UGS)、实时轮询业务(rtS)、非实时轮询业务(nrtPS)和尽力传输业务(BE)之间公平分配带宽,并保证各种业务的QoS特性,完成了在IEEE 802 16协议中留给用户自己定义的调度策略.     

一种基于紧急程度的自时钟开始时间公平排队分组调度算法

为了克服目前GPS (Generalized Processor Sharing)类调度算法中实时应用分组的排队时延较大且不稳定的局限性,该文提出一种新的分组排队调度算法,该调度算法在计算分组服务标签时添加了一个紧急程度函数,调整了到达分组间的竞争关系,从而可以按照实时性应用的要求来调整到达分组的转发先优级,由此显著降低了实时性应用分组的排队时延和抖动幅度。分析和仿真实验表明,与GPS类其它调度算法相比,该调度算法对于实时应用的分组能提供较低的、更稳定的排队时延保证,同时还继承了GPS类算法的公平性和排队时延有界等特性,而且对系统虚拟时间的跟踪计算更为简捷高效。     

A dynamic joint scheduling and call admission control scheme for IEEE 802.16 networks

We propose a dynamic joint scheduling and call admission control (CAC) scheme for service classes defined in IEEE 802.16 standard. Using priority functions, equipped with service weights and service arrival rates, the proposed scheduling scheme differentiates service classes from each other. Based on obtained priority values, we first allocate the achievable bandwidth proportionally. Within individual service classes, we then use appropriate local schedulers to transmit packets accordingly. Moreover, instead of immediate admitting or blocking a new connection request, the proposed CAC scheme computes the average transmission rate that can be allocated to that connection during a time interval. The connection is admitted if its required rate is satisfied while at the same time QoS requirements of ongoing connections are not violated. Our numerical results demonstrate the effectiveness of the proposed schemes compared to the other schemes in the literature.     

Using GI‐G‐1 queuing model for rtPS performance evaluation in 802.16 networks

Among the scheduling services, rtPS (real‐time polling service) is designated for real‐time applications. Among three packet delay intervals, performance effect on polling interval has been widely studied, but less on the intervals of scheduling and delivery. To evaluate the performance of delay‐sensitive rtPS applications, instead of using continuous queueing model, a discrete‐time GI‐G‐1 model, which considers intervals of polling, scheduling, and delivery, is proposed. By taking VoIP as a typical rtPS application, the transmission latency under different QoS settings, polling probability, and traffic load are presented. The latency is also compared among various codec schemes. The results indicate that when the codec rate is either fulfilled or dissatisfied by the promised bandwidth of service levels, the performance is highly dependent upon the polling probability, no matter what the traffic condition is. However, if the codec rate is in between the promised bandwidth of various service levels, the polling probability is a dominant factor in light traffic environment, while the settings on QoS parameters will strongly determine the performance in heavy traffic situation. In addition to the verification using simulation, the bandwidth utilization derived from the GI‐G‐1 model can be applied to improve the serving capacity of base stations. Copyright © 2011 John Wiley & Sons, Ltd.     

区分服务中AF类的一种调度算法

该文根据区分服务中确保转发(Assured Forwarding,AF)类的特点,设计了一种新的调度算法公平加权轮循(Fair、Weighted Round Robin,FWRR)算法。 FWRR是一种基于轮循、工作保持型、适于变长分组的调度算法.它的实现简单,算法复杂度为O(1).仿真实验和数学分析表明,FWRR算法不仅能够提供保证最小带宽的服务,而且能够按比例分配剩余带宽,适合用来调度区分服务中的AF类.     

Robustness Properties of FS-ALOHA++: A Contention Resolution Algorithm for Dynamic Bandwidth Allocation

This paper studies the robustness of FS-ALOHA++, a contention resolution algorithm used to reserve uplink bandwidth in wireless centralized LANs. The model takes into account errors on the contention channel, the capture effect and allows packets to arrive according to a general Markovian arrival process. Where channel errors and capture are typical for a wireless channel. Several analytical models are developed, using matrix analytical methods, allowing us to calculate the delay distribution of a request packet under different circumstances. Using these analytical models, we demonstrate that both FS-ALOHA and FS-ALOHA++ perform well under bursty and correlated arrivals. FS-ALOHA++ is shown to be more robust towards errors and capture. Moreover, it is concluded that implementing multiple instances of FS-ALOHA++ improves significantly the delays and sensitivity of the algorithm towards errors.