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。     

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。     

基于Matlab/Simulink下的TDMA协议在噪声环境中的仿真研究

时分多址(TDMA)接入是一种按时间划分节点传输信息的传输方式。本文利用Matlab/Simulink对TDMA(时分多址)协议进行了仿真研究,并对噪声环境下TDMA系统的抗干扰能力做出了分析研究。分析结果表明TDMA协议有良好地抗干扰能力。为TDMA在无线宽带接入网的应用提供了理论支持。     

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。     

光通信研究2013年第38卷第2期 目录

下一代PON(无源光网络)标准的研究尤其是MW-PON(多波长PON)已成为未来接入网发展的热点。文章描述了MW-PON系统在光层堆叠多个波长,以增加传统ODN(光分配网络)接入容量的独特思路,分析了MW-PON系统的波长分配、波长调谐、波长资源管理和波长通道性能监控等逻辑功能,重点研究了OLT(光线路终端)端口和ONU(光网络单元)设备功能实体、ONU正常激活和TDM/TDMA(时分复用/时分多址)激活、流氓ONU行为的减轻机制等关键技术。     

多波长PON体系结构研究北大核心

下一代PON(无源光网络)标准的研究尤其是MW-PON(多波长PON)已成为未来接入网发展的热点。文章描述了MW-PON系统在光层堆叠多个波长,以增加传统ODN(光分配网络)接入容量的独特思路,分析了MW-PON系统的波长分配、波长调谐、波长资源管理和波长通道性能监控等逻辑功能,重点研究了OLT(光线路终端)端口和ONU(光网络单元)设备功能实体、ONU正常激活和TDM/TDMA(时分复用/时分多址)激活、流氓ONU行为的减轻机制等关键技术。     

HFC接入网中多址接入技术与信道噪声特性的关系

目前 ,基于CableModem技术的HFC接入网已得到较为广泛的应用 ,但网络中的漏斗噪声限制了系统带宽的充分利用。着重分析上行信道的噪声特性 ,并根据噪声特性 ,研究了TDMA ,FDMA和CD MA 3种多址接入技术的特点 ,认为TDMA/FDMA混合方案更适合HFC网络上行信道的传输要求     

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．     

HFC接入网中多址接入技术与信道噪声特性的关系

目前,基于Cable Modem技术的HFC接入网已得到较为广泛的应用,但网络中的漏斗噪声限制了系统带宽的充分利用.着重分析上行信道的噪声特性,并根据噪声特性,研究了TDMA,FDMA和CDMA 3种多址接入技术的特点,认为TDMA/FDMA混合方案更适合HFC网络上行信道的传输要求.     

HFC接入网中多址接入技术与信道噪声特性的关系

目前,基于Cable Modem技术的HFC接入网已得到较为广泛的应用,但网络中的漏斗噪声限制了系统带宽的充分利用.着重分析上行信道的噪声特性,并根据噪声特性,研究了TDMA,FDMA和CDMA 3种多址接入技术的特点,认为TDMA/FDMA混合方案更适合HFC网络上行信道的传输要求.     

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.

     

Media access control for Ethernet passive optical networks: an overview

Medium access control is one of the crucial issues in the design of Ethernet passive optical networks. To ensure efficient transmission, an EPON system must employ a MAC mechanism to arbitrate access to the shared medium in order to avoid data collisions in the upstream direction and at the same time efficiently share the upstream transmission bandwidth among all ONUs. The purpose of this article is to provide a good understanding of the MAC issue, discuss the major problems involved (e.g., multiple access, bandwidth allocation, transmission scheduling, and quality of service support), and present an overview of the state-of-the-art solutions proposed thus far to the problems. It is also our purpose to motivate further studies on the problems described in this article     

Delay Aware Link Scheduling for Multi-Hop TDMA Wireless Networks

Time division multiple access (TDMA) based medium access control (MAC) protocols can provide QoS with guaranteed access to the wireless channel. However, in multi-hop wireless networks, these protocols may introduce scheduling delay if, on the same path, an outbound link on a router is scheduled to transmit before an inbound link on that router. The total scheduling delay can be quite large since it accumulates at every hop on a path. This paper presents a method that finds conflict-free TDMA schedules with minimum scheduling delay. We show that the scheduling delay can be interpreted as a cost, in terms of transmission order of the links, collected over a cycle in the conflict graph. We use this observation to formulate an optimization, which finds a transmission order with the min-max delay across a set of multiple paths. The min-max delay optimization is NP-complete since the transmission order of links is a vector of binary integer variables. We devise an algorithm that finds the transmission order with the minimum delay on overlay tree topologies and use it with a modified Bellman-Ford algorithm, to find minimum delay schedules in polynomial time. The simulation results in 802.16 mesh networks confirm that the proposed algorithm can find effective min-max delay schedules.     

The Key Technology in Optical OFDMPON

In this paper, a novel optical access network based on orthogonal frequency division multiplexing (OFDM) is proposed. An OFDM-based passive optical network (PON) uses multicarriers to carry different information that is transmitted to different optical network units (ONUs). In this paper, system performance is analyzed for OFDM-PON with different linewidths of the lightwave source, different optical signal-to-noise ratio (OSNR), different access distances, and different modulated formats. Colorlessness in the OFDM-PON is also analyzed. Finally, a 40 Gb/s baseband OFDM-PON with two carriers and achieve error-free performance over 25 km fiber transmission is proposed.     

基于宽带PON系统的高速以太网接入技术

基于宽带PON系统的高速以太网接入是将以太网与无源光纤接入网相结合,来实现以太网的高速,远距离接入,文章重点介绍了OSTS－2000系统的高速以太网接入技术,设备和性价比,以说明其巨大的应用前景。     

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.     

Resource Management for Broadband Access over Time-Division Multiplexed Passive Optical Networks

Passive optical networks are a prominent broadband access solution to tackle the "last mile" bottleneck in telecommunications infrastructure. Data transmission over standardized PONs is divided into time slots. Toward the end of PON performance improvement, a critical issue relies on resource management in the upstream transmission from multiple optical network units (ONUs) to the optical line terminal (OLT). This includes resource negotiation between the OLT and the associated ONUs, transmission scheduling, and bandwidth allocation. This article provides an overview of the resource management issues along with the state-of-the-art schemes over time-division multiplexed PONs (TDM-PONs). We categorize the schemes in the literature based on their features, and compare their pros and cons. Moreover, we introduce a unified state space model under which all TDM-PON resource management schemes can be evaluated and analyzed for their system level characteristics. Research directions are also highlighted for future studies.     

Ethernet PON (ePON): Design and Analysis of an Optical Access Network

With the expansion of services offered over the Internet, the last mile bottleneck problems continue to exacerbate. A passive optical network (PON) is a technology viewed by many as an attractive solution to this problem. In this study, we propose the design and analysis of a PON architecture which has an excellent performance-to-cost ratio. This architecture uses the time-division multiplexing (TDM) approach to deliver data encapsulated in Ethernet packets from a collection of optical network units (ONUs) to a central optical line terminal (OLT) over the PON access network. The OLT, in turn, is connected to the rest of the Internet. A simulation model is used to analyze the systems performance such as bounds on packets delay and queue occupancy. Then, we discuss the possibility of improving the bandwidth utilization by means of timeslot size adjustment, and by packet scheduling.     

A novel medium access control protocol for passive optical network supporting local area networking capabilities

An alternate solution for Ethernet passive optical networks (EPON) providing local area networking (LAN) capabilities is proposed in this article. Our solution adopts a star coupler-based PON architecture and uses radio frequency subcarrier multiplexed transmission for the LAN traffic delivery. The proposed medium access control (MAC) protocol supports a fully distributed control plane among the optical network units (ONUs) for ONU–ONU communication as well as upstream access to the OLT. The simulation results indicate that the proposed MAC protocol outperforms the others in terms of the average packet end-to-end delay, especially for LAN traffic.     

Novel multi-band DFT-spread OFDM-PON systems based on intensity modulation and direct detection for cloud computing

Passive optical network (PON) has become a preferable access technique for cloud computing due to its elastic bandwidth capacity and transmission stability. In particular, the orthogonal frequency division multiplexing PON based on intensity modulation and direct detection (IM/DD OFDM-PON) has gained extensive attention since it is a cost- and spectral-efficient system, while for the traditional IM/DD OFDM-PON, the use of OFDM could lead to the high peak-to-average power ratio (PAPR), and it is impossible to satisfy the different QoS degrees required by ONUs under a cloud environment. Thus in this paper, we design a novel multi-band discrete Fourier transform (DFT)-spread IM/DD OFDM-PON. The DFT-spread is utilized to reduce the PAPR; meanwhile, a multi-band power allocation and bit loading are achieved to satisfy the different degrees of QoS requirement owned by ONUs. The simulation results show that our system has the better performance of PAPR reduction compared with the traditional IM/DD OFDM-PON; meanwhile, the different QoS degrees of all ONUs are guaranteed.