一种半双工EPON接入方案

提出一种通过在星型耦合器的网络侧插入光纤布喇格光栅 ,在用户侧增加一个远端转发单元的方法 ,将CSMA/CD用作多址接入协议的半双工EPON接入方案。理论分析与仿真实验表明其性能与 10 0BASE T局域网相当。该方案实现简单 ,成本低廉 ,与现有以太网的体系结构兼容。     

一种实时无源光以太网的OAM设计与实现

设计了一种新型实时以太无源光纤网络(REPON)的OAM管理机制,包括新节点发现、配置、统计、故障管理功能,在FPGA平台上实现了相应REPON协议;搭建了一个包含Vxworks网管站、中心节点和接入节点的百兆实时光纤测试网络,对OAM各项管理功能进行了测试,验证了协议的可行性.     

光纤接入网络的业务需求和网络设计

<正> 宽带接入业务正处于从市场培育向快速发展过渡的关键时期。技术发展、业务创新、新价值链形成和创造性营销策略等因素彼此作用,共同构成电信运营商宽带业务竞争的利器。2003年第二季度,我国互联网用户持续增加,在运营商的大力推动下宽带接入用户更是发展迅猛,达713.7万,比2003年第一季度增长54.3％。其中xDSL用户数达421.1     

一种实时无源光以太网的硬件设计与实现

设计了一种基于无源光网络结构的实时光纤以太网的硬件系统,在FPGA的基础上实现了相应的中心节点与接入节点的物理层功能;构建了一个包含16个接入节点、1个中心节点的试验系统,进行了CAN实时业务的测试.测试结果验证了试验系统的可行性和实时性,实时响应时间小于200μs.     

一种实时以太网EtherCAT介绍

工业以太网技术一直以来都是工控领域一个热门的研究内容,国内外许多自动化公司已推出多种适合各自应用的工业以太网解决方案。EtherCAT技术以其高速简单、易于实现、实时性高等优点在多个领域取得了广泛应用。本文将从网络结构、寻址模式、通信帧格式、网络层协议等几个方面对EtherCAT网络做一个简单介绍。     

无源光网络用于以太网接入

介绍无源光网络（PON）的结构、业务接口、以太无源光网络（EPON）的工作原理以及管理、帧结构和光路设计，并对EPON提供的业务质量进行了分析，最后对EPON必须解决的几个关键技术难点进行了阐述。     

支持实时音频业务的以太网MAC协议

提出了一个被称为CSMA/PRI的改进MAC协议用于通过以太网技术向用户提供具有服务品质保证的实时音频业务.依靠减少同时竞争信道资源的工作站数目,所提出的方案改善了网络的传输效率,并缩减了平均的信道分配延时.通过分等级地进行网络资源预约和对不同类型的流量使用不同的碰撞解决算法,对比于现有的CSMA/CD和CSMA/RI协议,建议的改进方案能够向实时音频业务提供更加好的服务.     

光纤以太网接入实践

随着INTERNET的迅速发展,普遍的电话Modem已不能满足人们对上网速度的要求。本文通过对光纤以太网接入的实践,谈谈在现阶段适合县级有线台开展小区INTERNET宽带接入的技术方案及其优劣。     

宽带广覆盖光纤无线汇聚接入技术研究

三网融合对物理层网络架构提出了新的要求,有线接入的固有优势是可以实现超大容量接入,无线接入的突出特点是便捷,为了充分发挥二者的优势,有线与无线需要有机融合.对无线接入,要实现大容量必须提高无线载频的频率;对有线接入,国际上的发展趋势是传统的城域网与接入网合为一体,所以,未来的三网融合网络的物理网络架构必须具备长距离、广覆盖的特性.针对上述需求,本文提出了新型的面向三网融合的光载射频接入系统架构,阐述了光载射频接入系统的关键技术点和创新点.该方案实现电视、电话、宽带等信号在有线电视网络中一线传输,满足用户对海量电视、语音、数据业务的需求.     

基于实时以太网的图像传输系统的设计与实现

图像具有直观、方便和信息量丰富等特点,其网络传输已经渗透到了生产生活中的各个领域.为了满足日益增加的网络传榆信息量和速度要求,网络传输中采用实时操作系统和实时网络协议的技术受到越来越多的关注和应用研究,本文设计并实现了图像在实时操作系统RTAI和实时以太网RTnet环境中的传输.结果表明,通过实时网络协议RTnet传输同等信息的速度明显优于标准Linux网络协议栈.     

GPON的MAC协议设计

参照ITU T建议草案:吉比特无源光网络传输汇聚层规范(G.GPON.gtc),提出了一种支持分组业务接入的媒质接入控制(MAC)协议.通过仿真建模对该协议的性能进行了分析.     

WRAP: a medium access control protocol for wavelength-routedpassive optical networks

We describe the WDM request/allocation protocol (WRAP), a media-access control protocol for wavelength-routed passive optical networks (WR-PONs) in which each node has a single fixed optical receiver and a single tunable optical transmitter. The protocol does not require a carrier sensing capability, a separate control channel, or any centralized control or scheduling. Access to transmission channels is regulated by allocations made at destination nodes in response to requests made by source nodes. Computer simulation is used to investigate three different allocation algorithms, one of which-the preferential/random algorithm-is shown to provide significantly better performance than the alternatives. Simulations are presented comparing the performance of WRAP to two previously proposed applicable protocols-the interleaved time division multiple access (I-TDMA) protocol, and the FatMAC protocol. WRAP is shown to provide fair and flexible access to the transmission capacity, enabling high network utilization to be achieved under a wide range of traffic conditions, while providing a guaranteed minimum bandwidth between each source-destination pair. We conclude that of the three protocols considered here, WRAP is the best-suited to general-purpose data communications applications such as local, campus, and metropolitan area networks     

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     

On IEEE 802.14 medium access control protocol

In this article we present a comprehensive survey on the architecture, protocol issues, and standard of the hybrid fiber coaxial (HFC) networks which are evolving from the existing residential CATV networks. We first describe the HFC architecture and discuss the problems in providing two-way communication. Then, we identify three important medium access control (MAC) issues in designing the IEEE 802.14 standard; namely, synchronization, upstream channel access modes, and collision resolution. Resolutions adopted by the IEEE 802.14 Committee are illustrated after giving a protocol overview. Key resolutions include compensating round trip correction (RTC), interleaving minislots of data and request concurrently, and resolving collisions by multiple collision resolution engines, using the n-ary tree plus p-persistence algorithm with a first transmission rule. A comparative summary of some draft proposals that lead to the standard is given. Finally, we pinpoint two headend algorithms, minislot allocation and request scheduling, which are left open in the standard. They do not affect interoperability but may have a critical impact on performance.     

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.     

Mobility-aware timeout medium access control protocol for wireless sensor networks

Wireless sensor networks (WSNs), has been under development for a while by the academia and industry. Due to limited computational power, a typical sensor node may experience operational challenges. Moreover, mobility has become an important feature since emergency and healthcare related applications are evolving in WSNs. Consideration of mobile nodes in WSNs introduce new challenges for the designers. In this paper, an enhanced version of T-MAC protocol (a well-known medium access control protocol in WSNs) known as MT-MAC is proposed. Using the capturing fluctuation in RSSI and LQI values of the received SYNC packets, MT-MAC solves high packet drop ratio in T-MAC. By detecting the mobility, a mobile node softly handover to a new virtual cluster without losing connection with other nodes. The performance of the proposed solution is then compared with T-MAC, S-MAC as well as other well-known mobility-aware MAC (MS-MAC) protocol. The simulation results show that the proposed protocol significantly increases the throughput and packet delivery ratio of T-MAC in exchange for a small increase in power consumption. Compared to MS-MAC protocol, the proposed approach can reduce power consumption by 20–65%, and achieve slightly higher packet delivery ratio.