混合网络下双模ONU切换设计

随着三网融合、“光进铜退”国家政策推行和用户固网带宽需求增长,以EPON、GPON为代表的无源接入技术成为应用热点.国内PON网络以EPON、GPON共存,本文对E/GPON双模ONU做了研究,提出双模ONU的设计方案,市场应用前景广泛.     

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．     

EPON宽带接入技术及其应用前景

本文对EPON宽带接入网的体系结构和分层模型进行了初步分析,并对EPON的光传输、ONU的注册过程、时钟同步和测距、以及带宽分配等关键技术进行了论述,最后对EPON的应用前景进行了展望。     

EPON技术中影响ONU报文转发效率因素的研究

研究ONU报文转发效率的影响因素,有助于为用户提供高效优质的网络服务。文章研究的EPON(Ethernet Passive Optional Network,以太无源光网络)是一种基于以太网的PON技术,实现了光纤到户的传输方式,具有成本低,网速快等特点。EPON的传输架构是点到多点的形式,由OLT(Optical Line Terminal,光线路终端)与ONU(Optical Network Unit,用户网络单元)设备进行不断交互从而实现报文的转发。分光比和带宽分配是影响ONU报文转发效率的重要因素。不同的分光比光衰不同,对报文报文转发,带宽利用率产生影响;好的带宽分配算法不仅能保证用户体验良好,也可以尽可能的提高带宽利用率。     

以太网无源光网络中的时间标签法测距

基于千兆以太网的无源光网络将千兆以太网与无源光纤接入的优势相结合,实现低成本的高速、远距离接入。针对EPON系统上行链路多个ONU共享带宽的树型拓扑结构,为实现EPON系统上行TDMA接入,提出了时间标签法测距方案,论述了方案的可行性并指出其优点。     

一种延长EPON传输距离的方法

在以太无源光网络(EPON)系统中,光线路终端(OLT)和光网络单元(ONU)之间的最长光纤传输距离为20km,但在某些光纤到村(FTTV)之类的应用中,光纤线路的距离达到了80km甚至更远.文章提出了一种延长EPON系统传输距离的方法,它实现了一种适用于EPON系统的光功率放大器,且对EPON的注册发现窗口,上行带宽分配周期等参数进行了调整.     

EPON系统中ONU端口环路检测方案及实现

在以太网无源光网络(EPON)系统中,光网络单元(ONU)用户端口成环将会造成同一个无源光网络口下所有的业务中断。首先分析了EPON系统中ONU侧用户端口可能造成环路的主要原因及危害;然后提出了分别在OLT侧和ONU侧构造特殊报文进行环路检测的方案,并简要比较了它们的优缺点;最后对OLT侧环路检测方案的设计实现进行了重点描述。实践证明,采用OLT侧特殊报文检测方案能够有效地发现和防止ONU侧用户端口环路。     

异常发光ONU故障新型检测技术研究

异常发光ONU(光网络单元)故障严重影响EPON(以太无源光网络)的正常运行,已经成为危害EPON稳定运行的主要故障之一。文章通过对异常发光ONU故障检测技术的研究背景及故障原因的深入分析,提出一种基于硬件采集的新型异常发光ONU故障检测技术。该检测技术从硬件底层出发,对EPON网络进行链路层监测,为异常发光ONU的故障维修提供一套有效的解决方案。     

基于PAS6201的ONU硬件设计与实现

FTTH的光纤接入将是用户的终极接入方式,也是网络发展的必然趋势.无源光网络PON技术将成为实现FTTH的最佳网络结构,而EPON也将成为实现FTTH的最佳接入技术.文章基于PAS6201芯片完成了符合IEEE802.3ah标准的EPON ONU硬件平台的设计和开发.该硬件平台可以满足EPON ONU功能要求,且具有性能稳定、配置维护灵活的特点.     

基于EPON的带宽管理系统

基于以太网无源光网络(EPON)接入的按需分配带宽技术,结合EPON硬件的多逻辑链路技术和网管的带宽管理功能,提出了带宽模板的机制,并通过研发EPON带宽管理系统,实现了基于模板时间表驱动的带宽按需分配.文章对带宽管理系统的总体架构设计和功能实现进行了论述,并用测试结果验证了系统的设计目标.     

基于NGPON系统的ONU配置管理技术

根据中国电信EPON设备技术要求V2.1中介绍的ONU能力属性,提出NGPON系统中ONU配置管理技术。详细介绍了传统ONU配置管理技术以及ONU能力集配置管理技术实现过程。该方法能很好地解决设备间的互通问题,能很好地管理厂商生产的各种类型ONU,具有很强的实用价值。     

基于PON的宽带接入覆盖及接入模式研究

本文主要对以OLT的覆盖范围划分的综合业务接入区的规划进行了举例分析,并对PON的几种典型的接入模式进行了较为具体的研究。探讨了关于PON的基本建设思路。     

几种基于OFDM复用方式的无源光网络研究

文章介绍了3种十分常用的OFDM-PON(正交频分复用-无源光网络)结构:WDM(波分复用)-OFDM-PON、TDM(时分复用)-OFDM-PON和ECDM(码分复用)-OFDM-PON,并讨论了它们各自在传输速率、接收终端结构和频带利用率等方面的优势。     

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.     

A bandwidth scalable OFDM passive optical network for future access network

In order to reduce the cost for delivering the ever increasing broadband services, network providers need to simplify their network architectures and have a better control of the bandwidth. In this article, we propose a simple and cost-effective bandwidth scalable passive optical network (PON) based on orthogonal frequency division multiplexing (BSOFDM-PON). We report performance analysis in terms of the signal-to-noise ratio (SNR), bit-error-rate (BER), and error vector magnitude (EVM) of a PON system accommodating 32 optical network units (ONUs). Our simulations have successfully demonstrated that throughputs of 35.5 and 53.2 Gbps can be achieved using 16 and 64 QAM, respectively, within a total distance ranging from 20 to 30 km. It gives throughputs of 1.10 and 1.66 Gbps per ONU.     

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.     

WDM-PON无色ONU实现方法研究

WDM-PON是一种容量大、易升级、网络安全性高的新一代光接入网技术.文章简要分析了固定波长和可调谐波长的ONU实现方法,指出了其不足;重点研究了采用宽光源技术和无光源技术实现ONU的方法,指出无色ONU是构建WDM-PON的一种较理想的解决方案.     

一种基于PON技术的光传输系统方案设计

简要介绍了无源光网络(PON)的工作原理,提出了一种基于PON技术的光传输系统的系统组成,对系统的网络分布结构、传输方式、传输业务类型、帧结构、带宽分配、测距等方面的设计进行了说明,并给出了系统的OLT、ONU原理框图.     

DBA algorithm for the support of multi-tiered bandwidth guarantee in Ethernet passive optical networks

Access Networks based on Passive Optical Network (PON) technology can offer transport services to broadband service providers, such as mobile backhauling/fronthauling for Mobile Network Operators and multi-ONU Service Level Agreements for Virtual Network Operators. Besides that, Infrastructure Service Provider (InP) also provides broadband access services to end-users, such as residential subscribers and single or multi-site enterprises. In such a scenario, the InPs support diverse customers in the same PON. This paper proposes a bandwidth slicing mechanism to assure bandwidth isolation for different PON customers who rent part of a PON infrastructure from the InP. We introduce a Dynamic Bandwidth Allocation algorithm for Ethernet PONs called MAB-IPACT, which assures bandwidth on different granularity: conventional customers with a single ONU, multi-ONU customers owning a group of ONUs and providing a single type of service, and multi-ONU customers having diverse types of services. The MAB-IPACT algorithm also prioritizes bandwidth distribution among subgroups of ONUs of the same multi-ONU customer. A subgroup of ONUs is a subset of ONUs that belongs to the same multi-ONU customer, which are employed for the same type of service (e.g., ONUs for business service.). Simulation results show that the proposed mechanism improves the network performance of multi-ONU customers with subgroups of ONUs serving different services.

     

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.