新颖的WDM EPON动态带宽调度算法

对WDM EPON的ONU授权调度技术进行了研究,采用调度理论的方法来解决授权调度问题。将授权调度和波长分配进行结合,并将其形式化为矩形Packing问题,采用拟人的策略,提出了基于欧氏距离的高效用ONU带宽分配策略,为WDM EPON中ONU授权调度问题的快速求解提供了一种高效的启发式算法。进一步模拟实验表明,提出的算法可以减少平均分组时延,提高网络带宽利用率,表明算法对授权调度的有效性。     

一种支持多用户SLA的EPON上行带宽分配算法设计

在接入网服务等级协定的基础上,分析了以IPACT和CyclicDBA为代表的EPON上行动态带宽分配算法,讨论了其对EPON上多用户SLA支持所存在的固有缺陷。提出了适合SLA应用的EPON控制帧结构:授权帧和请求帧。根据这两种控制帧,设计了一种新型的支持多用户SLA的EPON上行信道带宽分配算法,等级轮询固定周期算法。通过理论分析和计算机仿真测试表明该算法针对EPON不同类型的接入用户均达到了较理想的性能指标,高优先级业务良好的时延和时延抖动特性,各种业务队列的尺度平稳,同时HPFCT还解决了传统轮询算法中低负载时下行带宽浪费明显的问题。     

EPON支持QoS的动态带宽算法研究

本文给出了一种支持多优先级业务的带宽分配算法。其中高优先级业务固定带宽分配和低优先级业务动态带宽分配，将上行帧分为第一时隙和第二时隙两部分，各ONU高优先级业务在上行第一时隙发送，第二时隙用于低优先级业务，同时采用固定周期的带宽分配方案，因此降低了高优先级业务的时延和时延抖动。通过ONU实行内部调度并且参与上行接入计算，避免了上行复杂的同步问题，提高了链路利用率。     

三网融合下的动态带宽分配方案研究

以三网融合的接八技术EPON为基础,分析三网融合后不同等级用户、不同等级业务的竞争关系,研完了已有的经典动态带宽分配方案,并根据ONU端不同用户的SLA（服务等级协议）划分,及ONU内部不同优先级业务的划分,设计了支持用户SLA的EPON系统,最后给出一种新的带宽分配算法STFD-DBA,并在理论上分析了该算法的可行性...     

EPON中支持多业务接入的动态带宽分配算法研究

以太网无源光网络(EPON)被视为下一代宽带接入网络(最后一公里问题)的最有吸引力的解决方案.EPON的一个主要特征是终端用户间共享上行信道,使用媒介接入控制方法来为不同流量类型提供多种服务.根据对已有的EPON上行带宽分配方案进行研究分析,并结合目前用户的多业务接入实际情况,提出了一种全面多业务接入的动态带宽分配的算法.     

一种新的EPON上行动态带宽分配算法与仿真

为了合理分配EPON上行信道带宽,提出一种能够区分服务等级的固定周期轮询动态带宽分配算法。该算法将光网络单元(ONU)的业务分为三个等级,根据不同的业务等级动态分配上行带宽,有效保证整个EPON网络的QoS以及带宽分配的公平性。同时,为了进一步提高EPON系统上行链路的带宽利用率,克服算法产生的idle time问题,对算法进行了改进。最后,对该算法进行仿真实验。     

混合TDM/WDM EPON中动态带宽分配算法

针对TDM EPON向WDM EPON升级过程中各个光网络单元(ONU)支持波长数不尽相同的特点,提出一种基于波长间负载均衡的动态带宽分配算法(LB-DBA).该算法在分配带宽时考虑波长信道的带宽约束,同时分两步确定授权给ONU的发送波长和发送时间,有利于波长信道间的负载均衡.仿真结果表明,LB-DBA可以避免已有算法在混合TDM/WDM EPON中可能出现的授权周期长度增加和资源利用率低等问题,有效改善网络性能.     

一种公平的EPON动态带宽分配算法

提出一种EPON上行链路动态带宽分配算法一周期比例DBA。ONU基于多门限周期地上报带宽请求，OLT根据ONU的带宽请求及其合约带宽进行动态带宽分配。当多个ONU竞争系统带宽时，OLT按照ONU合约带宽的比例进行带宽分配。仿真结果表明：周期比例DBA算法在实现高带宽利用率的同时又具有良好的公平性。     

基于动态最大传输窗口的带宽分配算法研究

数据业务和话音业务是未来网络中两个重要业务.作为下一代宽带接入的有效解决方案,以太网无源光网络(EPON)为用户提供了业务接口.对EPON中的上行带宽分配算法进行了分析研究,并提出一种基于动态最大传输窗口 DMTW 的 EPON 上行带宽分配算法.在本算法中根据业务和用户的优先级动态调整最大的传输窗口,合理分配上行带宽的资源,提高信道利用率和QoS,降低了传输时延.最后通过软件进行仿真,验证了算法的有效性.     

基于千兆以太网的无源光网络系统及其实现技术

以太网无源光网络EPON是目前光纤到户宽带接入的主流方式．时延补偿、动态带宽分配以及局端桥接等是构建EPON系统的关键技术．为了避免多个ONU发送冲突，实现用户端设备的时延补偿和自动加入，本文采用绝对时标来补偿不同光网络单元(ONU)往返时间的差异，完成其往返时间的计算和动态测距．上行链路动态带宽分配则采用基于逻辑链路标识(LLID)的流量统计算法，结合其服务水平协议(SLA)，获得了较低的延时特性和很高的带宽利用率．在EPON光线路终端(OLT)中借助动态过滤数据库技术实现了一个OLT和多个ONU的逻辑链路MAC仿真，解决了EPON和常规以太网IAN的兼容性问题．这些技术方案在武汉邮电科学研究院(WRI)完成的863科技攻关项目中均进行了严格的测试，结果符合预期要求．提供的现场测试数据表明研制的样机系统能很好支持多种业务的综合接入．     

Active intra-ONU scheduling with proportional guaranteed bandwidth in long-reach EPONs

The unused slot remainder (USR) problem in Ethernet Passive Optical Networks and long-reach Passive Optical Networks (LR-PONs) results in both a lower bandwidth utilization and a greater packet delay. In a previous study by the current group, an Active intra-ONU Scheduling with predictive queue report scheme was proposed for resolving the USR problem by predicting the granted bandwidth in advance based on the arrival traffic estimates of the optical network units (ONUs). However, it was found that the higher bandwidth prediction error in the proposed scheme prevents the network performance from being improved. Accordingly, the present study proposes a non-predictive-based ONU scheduling method designated as Active intra-ONU Scheduling with proportional guaranteed bandwidth (ASPGB) to improve the performance of LR-PONs. In the proposed method, the maximum guaranteed bandwidth of each ONU is adapted dynamically in accordance with the ratio of the ONU traffic load to the overall system load. Importantly, the proposed dynamic bandwidth allocation approach reduces the dependence of the network performance on the granted bandwidth prediction since the maximum guaranteed bandwidth determined by the Optical Line Terminal more closely approaches the actual bandwidth demand of each ONU. To solve the idle time problem arising in the event of an excess bandwidth reallocation, ASPGB is integrated with an improved early allocation (IEA) algorithm (a kind of Just-In-Time scheduling). The simulation results show that the IEA-ASPGB scheme outperforms previously published methods in terms of bandwidth utilization and average packet delay under both balanced and unbalanced traffic load conditions.     

Network coding based joint signaling and dynamic bandwidth allocation scheme for inter optical network unit communication in passive optical networks

As an innovative and promising technology, network coding has been introduced to passive optical networks (PON) in recent years to support inter optical network unit (ONU) communication, yet the signaling process and dynamic bandwidth allocation (DBA) in PON with network coding (NC-PON) still need further study. Thus, we propose a joint signaling and DBA scheme for efficiently supporting differentiated services of inter ONU communication in NC-PON. In the proposed joint scheme, the signaling process lays the foundation to fulfill network coding in PON, and it can not only avoid the potential threat to downstream security in previous schemes but also be suitable for the proposed hybrid dynamic bandwidth allocation (HDBA) scheme. In HDBA, a DBA cycle is divided into two sub-cycles for applying different coding, scheduling and bandwidth allocation strategies to differentiated classes of services. Besides, as network traffic load varies, the entire upstream transmission window for all REPORT messages slides accordingly, leaving the transmission time of one or two sub-cycles to overlap with the bandwidth allocation calculation time at the optical line terminal (the OLT), so that the upstream idle time can be efficiently eliminated. Performance evaluation results validate that compared with the existing two DBA algorithms deployed in NC-PON, HDBA demonstrates the best quality of service (QoS) support in terms of delay for all classes of services, especially guarantees the end-to-end delay bound of high class services. Specifically, HDBA can eliminate queuing delay and scheduling delay of high class services, reduce those of lower class services by at least 20%, and reduce the average end-to-end delay of all services over 50%. Moreover, HDBA also achieves the maximum delay fairness between coded and uncoded lower class services, and medium delay fairness for high class services.     

Inter‐ONU Bandwidth Scheduling by Using Threshold Reporting and Adaptive Polling for QoS in EPONs

I dynamic bandwidth allocation (DBA) scheme, an inter–optical network unit (ONU) bandwidth scheduling, is presented to provide quality of service (QoS) to different classes of packets in Ethernet passive optical networks (EPONs). This scheme, referred to as TADBA, is based on efficient threshold reporting from, and adaptive polling order rearranging of, ONUs. It has been shown that the network resources are efficiently allocated among the three traffic classes by guaranteeing the requested QoS, adaptively rearranging the polling orders, and avoiding nearly all fragmentation losses. Simulation results using an OPNET network simulator show that TADBA performs well in comparison to the available allocation scheme for the given parameters, such as packet delay and channel utilization.     

OSLG: A new granting scheme in WDM Ethernet passive optical networks

Several granting schemes have been proposed to grant transmission window and dynamic bandwidth allocation (DBA) in passive optical networks (PON). Generally, granting schemes suffer from bandwidth wastage of granted windows. Here, we propose a new granting scheme for WDM Ethernet PONs, called optical network unit (ONU) Side Limited Granting (OSLG) that conserves upstream bandwidth, thus resulting in decreasing queuing delay and packet drop ratio. In OSLG instead of optical line terminal (OLT), each ONU determines its transmission window. Two OSLG algorithms are proposed in this paper: the OSLG_GA algorithm that determines the size of its transmission window in such a way that the bandwidth wastage problem is relieved, and the OSLG_SC algorithm that saves unused bandwidth for more bandwidth utilization later on. The OSLG can be used as granting scheme of any DBA to provide better performance in the terms of packet drop ratio and queuing delay. Our performance evaluations show the effectiveness of OSLG in reducing packet drop ratio and queuing delay under different DBA techniques.     

一种新的基于GPON的动态带宽分配算法

为了实现吉比特无源光网络(GPON)带宽分配的公平性,降低网络的丢包率及传输延时,文章研究了GPON系统传输汇聚层的帧结构及动态带宽分配的实现方法,提出了一种新的动态带宽分配(DBA)算法--基于QoS的二层动态带宽分配算法.基本思路是根据不同等级业务的带宽需求,在PON层和ONU层分别进行带宽的合理分配.理论分析和仿真试验证明,这种算法可以提高带宽的利用率,保证不同业务的不同时延要求,并且对不同用户和不同等级的业务都具有很好的公平性.     

Comprehensive bandwidth utilization and polling mechanism for XGPON

For an efficient utilization of the upstream bandwidth in passive optical network, a dynamic bandwidth assignment mechanism is necessary as it helps the service providers in provisioning of bandwidth to users according to the service level agreements. The scheduling mechanism of existing schemes, immediate allocation with colorless grant and efficient bandwidth utilization (EBU), does not assign the surplus bandwidth to a specific traffic class and only divides it equally among the optical network units (ONUs). This results in overreporting of ONU bandwidth demand to the optical line terminal and causes wastage of bandwidth and increase in delays at high traffic loads. Moreover, the EBU also assigns the unused bandwidth of lightly loaded ONU queues to the overloaded queues through an Update operation. This Update operation has a flaw that it borrows the extra bandwidth to a queue in the current service interval, if the queue report is higher than its service level agreement and refunds in next service interval. This borrow‐refund operation causes reduced bandwidth allocation to the lower priority classes and increases their delay and frame loss. This study improves both these weaknesses. The simulation results show that the proposed scheme uses bandwidth efficiently and reduces mean upstream delay of type‐2 (T2) traffic class by 38% and type‐3 (T3) up to 150% compared to immediate allocation with colorless grant at a cost of up to 10% higher delay for T2. However, T4 performance improves by 400% compared to EBU with slight increase in delay for T2 traffic class. Overall, it shows a balanced performance for all the traffic classes and minimizes the bandwidth waste per cycle as well as the frame loss rate.     

Architecture of multi-OLT PON systems and its bandwidth allocation algorithms

In this paper, we propose a novel passive optical network (PON) architecture that has multiple optical line terminals (OLTs). Unlike existing PONs where all ONUs are connected to a single OLT, the proposed multi-OLT PON allows subscribers to choose their own service providers from among multiple OLTs. Service companies and subscribers can make service level agreements (SLA) on the amount of bandwidth that each OLT or ONU requires. A new control protocol and bandwidth allocation algorithms appropriate in this new PON environments are suggested. For the downstream, a scheme to share the bandwidth among multiple OLTs is studied to maximize the total transmitted packets while guaranteeing each OLT’s SLA. A modified Limited Dynamic Bandwidth Allocation named mLimited scheme is also proposed for upstream transmission toward multiple OLTs, which maximizes the total upstream throughput while minimizing the delay of each ONU. Performances of the proposed PON architecture and algorithms are analyzed. A PON system with two OLTs and 16 ONUs is used in the analysis. Self-similar traffic reflecting current packet distribution is used in the packet generation. The results show that the proposed DBA schemes efficiently manage bandwidth even when the occurred traffic load is quite different from the reserved bandwidth. It is found that the proposed PON architecture is appropriate in supporting diverse services in future high-speed optical access network.     

Wavelength channel minimization-based energy-aware mechanism in a multichannel EPON

We propose an energy-aware mechanism (EAM) applicable to the multichannel Ethernet Passive Optical Network that can minimize the number of wavelength channels used and save energy. Wavelength channel minimization is processed by collecting the information such as request message, allocated grant, and start time of each optical network unit (ONU) transmission in the previously elapsed scheduling cycles and comparing it with the buffer occupancy and packet delay conditions of the ONUs required by the user’s quality-of-service requirement. They are exchanged between the optical line terminal (OLT) and the ONUs via the multipoint control protocol. In this way, at the beginning of each scheduling cycle, the ONU’s buffer occupancy and packet delay conditions can be evaluated, and then, the OLT decides the smallest number of wavelength channels to be used in the current scheduling cycle. By turning off the OLT receivers corresponding to the unused wavelength channels, the OLT can save energy. The performance of the proposed EAM was evaluated through simulations using nonjoint off-line dynamic bandwidth allocation and dynamic wavelength assignment algorithms. The results showed that the OLT receivers’ power consumption could be reduced by 48 % on average.     

一种新的基于认购速率和QoS等级的动态带宽分配算法

为了实现吉比特无源光网络带宽分配的公平性,降低网络的传输延时,设计了一种新的媒质访问控制协议,提出了一种新的动态带宽分配算法.其基本思想是:在保证拥有不同QoS业务的用户得到认购速率的基础上,根据网络负载的大小,动态地将某些用户未使用的带宽分配给其他带宽需求大的用户,以提高网络的带宽利用率.仿真结果表明,这种新的算法在严格控制数据传输延时的前提下,能够保证多用户之间带宽分配的公平性.     

Just-in-Time Scheduling for Multichannel EPONs

We investigate optical network unit (ONU) grant scheduling techniques for multichannel Ethernet passive optical networks (EPONs), such as wavelength division multiplexed (WDM) EPONs. We take a scheduling theoretic approach to solving the grant scheduling problem. We introduce a two-layer structure of the scheduling problem and investigate techniques to be used at both layers. We present an extensive ONU grant scheduling simulation study that provides: 1) insight into the nature of the ONU grant scheduling problem and 2) indication of which scheduling techniques are best for certain conditions. We find that the choice of scheduling framework has typically the largest impact on average queueing delay and achievable channel utilization. An offline scheduling framework is not work conserving and consequently wastes channel resources while waiting for all ONU REPORT messages before making access decisions. An online scheduling framework, although work conserving, does not provide the best performance since scheduling decisions are made with the information contained in a single ONU REPORT. We propose a novel online just-in-time (JIT) scheduling framework that is work conserving while increasing scheduling control by allowing the channel availability to drive the scheduling process. In online JIT, multiple ONU REPORTs can be considered together when making scheduling decisions, resulting in lower average queueing delay under certain conditions and a more effective service differentiation of ONUs.