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.     

WDM EPON的OPNET建模和算法仿真

提出了WDM EPON的一种基于OPNET的建模方法,并且搭建了WDM EPON的仿真平台.在该平台上实现了Online算法,并且分别采用固定服务、限制服务、开门服务三种带宽分配策略进行仿真测试.仿真结果表明在WDM EPON的架构下,Online算法采用开门服务策略会得到较低端到端延时、较高的带宽利用率以及ONU处较小的队列长度.     

MRMC:一种高效的EPON动态带宽分配方案

提出一种高效的EPON动态带宽分配方案,即多标准带宽请求动态带宽分配方案(MRMC).MRMC采用分步请求/集中授权的轮询机制,ONU向OLT提出多个基于不同标准的带宽请求,OLT权衡选择授权带宽.该分配方案既考虑了ONU适时队列负载情况,又解决了阻塞帧问题,同时兼顾了公平性原则,进一步提高了EPON的工作效率.     

EPON中保证QoS的动态带宽分配算法

作为一种新技术，EPON系统采取在下行信道使用广播方式而在上行信道使用时分多址(TDMA)方式，为用户提供共享传输介质的接入方式，因此就需要一种接入控制机制来为用户分配带宽。为了使EPON系统更好地支持QoS并且进一步提高带宽利用率，提出了一种新的固定周期轮询动态带宽分配算法，针对不同时延特性业务采用不同的授权分配算法。算法包括两部分：OLT时ONU的调度以及ONU内部不同优先级的队列之间的调度。最后讨论了包时延、系统吞吐量等仿真结果和性能分析。     

WDM—PON：1G带宽如何打造

PON按信号分配方式可以分为功率分割型无源光网络（PSPON）和波分复用型无源光网络（WDM—PON）。目前,APON、BPON、EPON、GPON均属于PSPON。PSPON采用星型耦合器分路,上／下行传送采用TDMA／TDM方式,实现共享信道带宽,分路器通过功率分配将OLT发出的信号分配到各个ONU上。WDM—PON则是将波分复用技术运用在PON中,光分路器通过识别OLT发出各种波长,将信号分配至日各路ONU,     

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。     

支持多业务预测机制的EPON动态带宽分配算法

针对IPACT算法中存在较严重的轻载惩罚现象,提出了一种支持多业务预测机制的动态带宽分配算法(eIPACT算法).通过估计两个连续轮询之间的不同业务分组的到达量,并给ONU授权额外的带宽,减少了ONU分组中的等待时间和缓存占用.采用多业务优先级调度策略,不仅能避免轻载惩罚还可以保证系统的服务质量.结果表明,该算法既极大...     

EPON带宽分配算法设计原则研究

在分析多种算法的基础上,对以太无源光网(EPON)动态带宽分配(DBA)算法的设计原则进行了总结.提出ONU分组交织、基于以太帧边界授权、采用较大的轮询周期等三项措施,来提升高信道利用率.提出采用两级结构的DBA为用户分别授权,在支持QoS的同时保障用户间的公平性.基于上述设计原则,提出了一种新算法──面向用户基于帧边界分配算法(SOABR),仿真实验证实其具有极高的信道利用率、良好的延时性能和公平性.     

支持多业务的EPON动态带宽分配算法

EPON的关键技术之一是动态带宽分配(DBA)问题。为了支持语音、视频、数据等多业务和保证不同的服务质量(Qo S)和有效克服轻载惩罚问题,本文提出了一种支持多业务的EPON动态带宽分配算法。通过对ONU侧的业务按照优先级进行区分,对到来的业务按照严格的优先级排队,以此保证高优先级业务的时延要求;引入预测避免出现了轻载惩罚,在OLT侧预测高优先级业务的到来情况,为ONU多分配预测的带宽大小。实验表明,本文算法提高了网络的服务质量。     

EPON系统的动态带宽分配算法

针对EPON系统上行链路多个ONU共享带宽的拓扑结构,分析了制定带宽分配策略所需考虑的基本因素,介绍了一种新的动态带宽分配算法,通过动态请求分配机制,实现上行链路的高效利用。     

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.     

Traffic scheduling in hybrid WDM–TDM PON with wavelength-reuse ONUs

Hybrid WDM?CTDM PON (wavelength division multiplexing?Ctime division multiplexing passive optical network) that applies wavelength-independent or colorless ONU (optical network unit) technologies will further reduce implementation and maintenance expenses. The ??wavelength-reuse?? colorless ONU technology imposes a physical constraint in the hybrid WDM?CTDM PON that the same wavelength is used for both upstream and downstream traffic transmission of an ONU. This physical constraint brings a new challenge to developing traffic scheduling algorithms in the network, as upstream traffic scheduling is no longer independent of downstream traffic scheduling and the existing traffic scheduling algorithms that treated the upstream and downstream traffic independently cannot be applied in this case. We propose a new traffic scheduling algorithm that takes both directions?? traffic scheduling into account at the same time. A logical PON concept is defined, and wavelength resource sharing is performed based on reconfiguring logical PONs. Simulation study on this algorithm is conducted, and results show that it achieves efficient wavelength and bandwidth resource sharing in the network.     

一种基于 SLA 的 WDM EPON 动态波长带宽分配算法简

波分复用技术结合时分复用形成了混合WDM EPON,如何提高系统的带宽利用率和用户服务质量成为关键技术。结合已有算法的优缺点,提出一种新的动态波长带宽分配算法。该算法结合业务等级分类和用户服务等级协议的权重为光网络单元分配相应的带宽和波长,以达到提高服务质量、带宽分配公平性,提高上行带宽利用率和改善网络性能的目的。     

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.     

Grant-sizing-differentiated bandwidth allocation algorithm for the coexistence of ONUs with and without wavelength tunability in WDM/TDM PONs

Adopting the pay-as-you-grow approach to upgrade passive optical network (PON) facilities by WDM technology insures the smoothness of the upgrade, and also results in the coexistence of wavelength-fixed/tunable optical network units (ONUs) in WDM/TDM PONs. Dynamic bandwidth allocation (DBA) is the key to support such coexistence of heterogeneous ONUs. Thus, DBA is also the key to support the smooth evolution of PONs. To more fairly coordinate the bandwidth allocation among the coexisting heterogeneous ONUs, a differentiated grant sizing (DGS) scheme is proposed. In DGS, not only the fairness between the wavelength-fixed/tunable ONUs but also the fairness between the lightly/heavily loaded ONUs is taken into account. To further carry out load balancing among wavelengths, a grant scheduling scheme is also proposed to cooperate with the grant sizing scheme. In the grant scheduling scheme, a measure of the ONUs’ flexibility is given, and then the least flexible job first rule (LFJF) is adopted for joint wavelength and time-slot assignment. Finally, to demonstrate the effectiveness of the proposed algorithm, a series of comparative analyses is conducted based on simulation experiments.     

一种带EOC网管功能的新型ONU模块设计

因为传统的ONU和EOC网管单元都是分开设计的,硬件上采用两套不同的CPU管理芯片,存在网管成本高的问题,所以该文介绍了一种集成EOC网管功能的ONU模块。该ONU协议芯片采用高通公司的OPL-06750,它是一款内部集成32位MIPS24KEcTM内核的微处理器,结合高通公司的AR8327千兆交换芯片可以构建传统千兆ONU模块,同时通过在软件上采用ONU、EOC网管双进程设计的方法可以统一地管理ONU和EOC网络设备,省去了EOC网管单元CPU。该模块具有成本低廉、性能稳定、配置维护灵活的特点,适用于广电运营商的EPON+EOC双向网改造。该文给出了ONU模块的硬件组成框图和ONU、EOC设备拓扑关联的软件流程。     

EPON中基于NIOS的ONU设计

提出一种基于ALTERA公司的NIOS嵌入式微处理器的ONU(光网络单元)设计方案.通过将NIOS软核处理器、自定义逻辑模块、存储器和I/O集成到单块低成本的FPGA上,组成一个SOPC(片上可编程系统),实现以太网无源光网络中的ONU功能.与采用套片加软件来实现ONU的方案相比,该方案降低了系统的成本,复杂性和功耗.     

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.