Enhanced Dynamic Bandwidth Allocation Algorithm in Ethernet Passive Optical Networks

As broadband access is evolving from digital subscriber lines to optical access networks, Ethernet passive optical networks (EPONs) are considered a promising solution for next generation broadband access. The point‐to‐multipoint topology of EPONs requires a time‐division multiple access MAC protocol for upstream transmission. In this paper, we propose a new enhanced dynamic bandwidth allocation algorithm with fairness called EFDBA for multiple services over EPONs. The proposed algorithm is composed of a fairness counter controller and a fairness system buffer in the optical line terminal. The EFDBA algorithm with fairness can provide increased capability and efficient resource allocation in an EPON system. In the proposed EFDBA algorithm, the optical line termination allocates bandwidth to the optical network units in proportion to the fairness weighting counter number associated with their class and queue length. The proposed algorithm provides efficient resource utilization by reducing the unused remaining bandwidth made by idle state optical network units.     

Priority-based dynamic bandwidth allocation in Ethernet Passive Optical Networks

In this article, new Dynamic Bandwidth Allocation (DBA) algorithms which give high priority to some ONUs corresponding to important agencies are studied in order to manage emergency cases causing severe network traffic. In order to deal with such cases, the network state is divided into two states, namely the normal and the emergency states. We apply the Weighted Round Robin (WRR)-based algorithm to the normal state, and three priority-based DBA algorithms are applied to the emergency state. These algorithms are different from each other according to the mode of protecting non-priority ONUs from starving. Each algorithm is analyzed in terms of utilization of the uplink bandwidth and the average packet delay. Simulation and theoretical results show that the proposed algorithms are working properly at the emergency state and can satisfy more stringent QoS requirements than WRR algorithms.

An AWG-based WDM-PON architecture employing WDM/TDMA transmission for upstream traffic with dynamic bandwidth allocation

In this article, we examine a candidate architecture for wavelength-division multiplexed passive optical networks (WDM-PONs) employing multiple stages of arrayed-waveguide gratings (AWGs). The network architecture provides efficient bandwidth utilization by using WDM for downstream transmission and by combining WDM with time-division multiple access (TDMA) for upstream transmission. In such WDM-PONs, collisions may occur among upstream data packets transmitted simultaneously from different optical networking units (ONUs) sharing the same wavelength. The proposed MAC protocol avoids such collisions using a request/permit-based multipoint control protocol, and employs a dynamic TDMA-based bandwidth allocation scheme for upstream traffic, called minimum-guaranteed maximum request first (MG-MRF), ensuring a reasonable fairness among the ONUs. The entire MAC protocol is simulated using OPNET and its performance is evaluated in terms of queuing delay and bandwidth utilization under uniform as well as non-uniform traffic distributions. The simulation results demonstrate that the proposed bandwidth allocation scheme (MG-MRF) is able to provide high bandwidth utilization with a moderately low delay in presence of non-uniform traffic demands from ONUs.     

以太网无源光网络的服务质量分析

以太网无源光网络正成为当前光接入网研究的热点课题．本文重点研究了服务质量问题。在分析EPON系统QoS问题的基础上，利用优先级排队理论对基于QoS的DBA算法的性能进行了理论分析，指出DBA算法进一步优化的方向。     

ONU buffer reduction for power efficiency in Passive Optical Networks

Power efficiency will be one of the primary factors dictating the choice of future network deployments. Passive Optical Networks (PONs) in general consume less power and are well positioned to be the technology of choice for future access networks. In a PON, the Optical Network Units (ONUs), that provide the interface between the end user and the Optical Line Terminal (OLT), consume a substantial amount of power. Typically, 2 MB or more buffer capacity is used in an ONU for holding upstream packets. This consumes around 1.29 W of leakage power when idle. In the current work, we show the relationship between buffer capacity and leakage power consumption. This motivated us to propose buffer reduction as a strategy to reduce power consumption of an ONU. We propose three schemes viz. Zero Buffers (ZBs), Node Proportional Buffers (NBs) and Rate Proportional Buffers (RBs). They impose aggressive buffer capacity restrictions on the ONU to reduce power consumption. Having said that, these schemes cannot be realized without modifications to the basic network operation. We propose mechanisms required to support the buffer reduction schemes. Through simulations we explore the relationship between power consumption and network performance. We also present the comparison of the proposed schemes in terms of network performance with different network loads. Simulation results indicate that despite buffer size reduction, an acceptable level of application level performance can be achieved. We show that buffer reduction as a strategy is viable and can cut down more than 90% of leakage power consumed by packet buffers at the ONU.     

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.     

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。     

Ethernet PONs: a survey of dynamic bandwidth allocation (DBA) algorithms

Optical networks are poised to dominate the access network space in coming years. Ethernet passive optical networks, which leverage the ubiquity of Ethernet at subscriber locations, seem destined for success in the optical access network. In this article we first provide a brief introduction to Ethernet passive optical networks, followed by a discussion of the problem of dynamic bandwidth allocation. We then introduce a framework for classifying dynamic bandwidth allocation schemes and provide a comprehensive survey of the dynamic bandwidth allocation methods proposed to date. We conclude with a side by side comparison of the schemes based on their most prominent characteristics, and outline future developments of dynamic bandwidth allocation schemes.     

一种保证QoS的EPON上行动态带宽分配算法

文章提出了一种新的保证服务质量(QoS)的EPON上行动态带宽分配算法,该算法根据区分服务(Diffserv)模型和服务等级协定(SLA)确定光网络单元(ONU)的带宽分配权重,根据数据QoS的不同分配不同的优先权,这样不但确保了各个ONU的带宽分配和QoS,而且可以满足一些高优先级业务的要求.同时,文章还提出了相应的多点控制协议(MPCP)控制消息格式.     

EPON中节能动态带宽分配算法

结合光网络单元(ONU)休眠控制和动态带宽分配机制,提出一种节能的双向DBA算法。该算法根据上/下行业务量为每个ONU分配合适的上/下行授权带宽,保证每个ONU在上/下行方向都具有较低的传输时延,同时尽可能增加ONU的休眠时间来降低网络能耗。仿真结果表明,与已有算法相比,该算法具有较低的上/下行平均时延,并能减少ONU的能耗。     

Hierarchical Dynamic Bandwidth Allocation Algorithm for Multimedia Services over Ethernet PONs

In this paper, we propose a new dynamic bandwidth allocation (DBA) algorithm for multimedia services over Ethernet PONs (passive optical networks). The proposed algorithm is composed of a low‐level scheduler in the optical network unit (ONU) and a high‐level scheduler in the optical line terminal (OLT). The hierarchical DBA algorithm can provide expansibility and efficient resource allocation in an Ethernet PON system in which the packet scheduler is separated from the queues. In the proposed DBA algorithm, the OLT allocates bandwidth to the ONUs in proportion to the weight associated with their class and queue length, while the ONU preferentially allocates its bandwidth to queues with a static priority order. The proposed algorithm provides an efficient resource utilization by reducing the unused remaining bandwidth caused by the variable length of the packets. We also define the service classes and present control message formats conforming to the multi‐point control protocol (MPCP) over an Ethernet PON. In order to evaluate the performance, we designed an Ethernet PON system on the basis of IEEE 802.3ah “Ethernet in the first mile” (EFM) using OPNET and carried out simulations. The results are analyzed in terms of the channel utilization, queuing delay, and ratio of the unused remaining bandwidth.     

支持QoS的多链路最少变换动态带宽分配算法

提出一种支持QoS的多链路最少变换动态带宽分配方法（MCDBA）,该方法实现了支持不同的QoS等级,量化了带宽分配的大小,在满足一定QoS限制的条件下最小化带宽分配变换次数。仿真结果验证了MCDBA能有效地减少数据分组的时延和提高系统的带宽利用率,MCDBA可用于解决大规模网络链路接入的复杂QoS控制的实际问题。     

同步无线Mesh网络带宽申请与分配策略的改进

数据通信具有突发性与带宽计算的不确定性,现有同步无线Mesh网络带宽申请与分配策略未对此问题进行充分考虑,在设计上存在带宽申请速度慢、带宽分配没有最大化、将数据时隙区分了上下行等不足,导致了QoS保障能力低与网络性能的下降。提出了带宽申请与分配策略的改进方案,包括结合各类数据业务类型的带宽申请条件的描述、检查数据发送队列的时间间隔描述、带宽分配最大化的描述、数据时隙不再区分上、下行的描述。理论分析表明,改进后的方案能够提供精确的QoS保障并提高网络性能。     

一种基于星上处理的卫星ATM网络动态带宽分配策略

本文提出了一种基于星上处理的卫星ATM网络的动态带宽分配方案,它通过对流量的估计动态申请带宽,卫星作为控制中心根据链路利用情况来分配带宽,仿真结果表明,相对于现有的的方法,它可以保持链路效率,提高业务的服务质量,同时这种方法对星上资源要求不高,易于实现。     

GPON系统中基于QoS的动态带宽分配算法的研究

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,研究了GPON系统传输汇聚层的帧结构及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.性能分析与对比表明,这种算法对不同用户和不同等级的业务都具有很好的公平性,并可以降低低等级业务的传输延时.     

硬件支持的多虚拟机数据交换及动态带宽分配方法

针对同一宿主计算机上多虚拟机之间数据交换开销大且带宽分配不灵活的问题,提出了一种硬件支持的多虚拟机数据交换及动态带宽分配方法,并进行建模和实验.该方法釆用IO虚拟化的思想,面向以太网控制器的硬件架构进行改进与优化.通过对虚拟机的发送数据进行解析,同时扩展发送引擎对接收BD环的访问权限,实现数据从发送引擎直接向目的虚拟机接收队列的交换过程;通过对虚拟机中接收队列的数据信息进行统计与分析,实现对各个虚拟机的带宽进行动态分配与调整.以自主研发的千兆以太网控制器为原型搭建测试平台进行实验.结果表明,本文提出的方法不仅减小了多虚拟机之间数据交换和带宽分配的CPU开销,而且对以太网控制器和虚拟机管理程序均保持了兼容.     

EPON中安全机制的研究

基于以太网的无源光网络(EPON)是一个点到多点的系统,面临着很多安全隐患。针对EPON系统中存在的几种安全威胁,提出了一种解决EPON安全隐患的综合性方案。     

一种改进的GPON动态带宽分配策略

利用小波变换将自相似性网络流量的长相关性转化为短相关性,并预测流量的方法,对GPON系统物理媒质控制(MAC)层的关键技术--动态带宽分配(DBA)进行研究.在理论上对一种已有的DBA策略提出合理改进.     

无源光网络标准发展及关键技术研究

无源光网络(Passive Optical Network,PON)作为当今接入网的主要技术解决方案,具有带宽使用效率高、传输距离远、抗干扰能力强等特点.通过研究PON技术的发展动态,本文首先归纳了各种PON技术的产生背景和应用特点,整理出各技术间的连接关系及主要标准;其次介绍了PON技术的帧结构,并对带宽、波长、传输模式等PON技术的主要参数进行了汇总;然后将国内外研究热点进行划分,围绕媒体访问控制协议、帧结构、动态带宽分配算法、节能机制等关键技术,阐述了其研究现状及在PON中的重要作用;最后对PON技术的发展趋势进行了展望.