分组网络的同步技术发展趋势

介绍了分组网络的同步相关标准;结合分组传送设备目前支持的同步技术,分析了分组网络的引入对同步网组网的影响;探讨了分组同步技术的发展趋势。     

基于SDH的PTP时间同步技术实现

介绍了基于SDH网络利用PTP技术恢复频率和时间性能的验证测试,介绍了分组网络中PTP频率同步和时间同步的技术,分析了在SDH网络中传送PTP与在分组网络中传送PTP的不同点。     

PTN组网模式下的TD-SCDMA基站同步问题探讨

分组传送网(PTN)是具备传送功能的分组化网络,主要用于解决无线接入网(RAN)的IP化承栽.因此研究其时间同步问题具有重要意义.文章介绍了PTN的同步需求和IEEE 1588同步技术,描述了PTN传送时间同步的要求和方式,探讨了PTN组网模式下时分同步码分多址(TD-SCDMA)基站同步的解决方案.     

PTN时钟同步技术及应用

时钟同步是分组传送网（PTN）需要考虑的重要问题之一。可以采用同步以太网、IEEE1588v2、网络时间协议（NTP）等多种技术实现时钟同步。同步以太网标准的同步状态信息（SSM）算法存在时钟成环,以及难以对节点跟踪统计的问题。中兴通讯提出了一种扩展SSM算法可以改进时钟同步问题。在时间同步方面,由于NTP的精度还无法满足电信网的需求,仅采用1588v2又会带来收敛时间较慢、在网络负载较重时时间延迟精度容易受到影响等问题。中兴通讯提出了同步以太网基础的1588v2时间传递方案,对提高PTN网络中时间同步的精度起到了较好的作用。     

关于PTN时钟同步技术及其应用

随着业务的IP化,驱动网络向IP化发展为大势所趋,而分组传输网(PTN)是传输网的主流IP承载技术,时钟同步又是分组传送网络(PTN)中最重视的问题。文章通过对PTN的主流技术和时钟同步的相关介绍,对PTN时钟同步技术的具体应用及应用意义进行了研究与讨论。     

分组传送网（PTN）技术及发展

 本文通过市场需求和网络融合发展趋势,分析了分组传送网产生和发展的原因。阐释了分组传送网的关键技术,包括PTN架构、业务、OAM、QoS、生存性技术、同步技术、控制技术、交换技术等。描述了分组传送设备的类型和功能特性及在网络中的应用。文中还对分组传送网有关标准尤其是MPLS-TP相关标准的发展情况进行了介绍。通过对需求、技术、应用、标准几个方面情况,可以理解分组传送网的发展趋势。     

分组传送网中时钟同步技术的研究

随着下一代网络(NGN)和3G网络的大规模应用,传统的以电路交换为主的公共交换电话网(PSTN)逐渐转向以分组交换为主.在从传统网络向未来网络转换的过程中,时钟同步仍然是其中面临的一大难题.文章研究和分析了分组传送网(PTN)中应用同步的两种技术,即同步以太网技术和IEEE 1588 V2技术,并且阐述了其相关原理和在PTN时钟同步中的应用.     

分组网络同步技术的标准化进展

介绍了基于分组网络的频率同步标准和时间同步标准的发展历程,分析了分组频率与时间同步标准的最新进展,最后对分组同步标准今后的发展方向进行了阐述。     

PTP技术分析与应用

在通信系统全网IP化的大背景下,分组网络作为统一承载网将面临新的同步需求问题。传统的同步技术精度较低,无法满足新应用对高精度同步的需求。IEEE 1588标准精密时间同步协议(PTP)的提出,成为一种有效解决高精度同步问题的方案。首先分析了PTP技术的同步原理,接着通过综合比较当今几种常用的同步技术的特点得出PTP技术的优势,最后提出了应用方案,并分析了实施过程和部署灵活性。PTP技术可方便灵活地应用于分组网络中,同步精度可达亚微秒级,将成为GPS的有效替代。     

PTN时钟同步技术的探讨

随着分组传送网（PTN）逐步成为统一的多业务分组传送网络,PTN时钟同步技术成为业界越来越关注的焦点之一。本文对从时钟同步的概念出发,对PTN常用的时钟同步技术,如自适应时钟恢复技术（ACR）,同步以太网和IEEE 1588v2,做了介绍和探讨。     

The open-ring/active-bus network structure: access techniques andtheir heavy-traffic performance

The open-ring/active-bus network structure for packet-switched, multiple-access communication over high-speed fiber-optic networks is studied. The structure is shown to suffer from fewer synchronization constraints than a closed ring structure and to provide a capacity greater than unity because it allows reuse of channel bandwidth. Various access mechanisms on this structure are discussed, and their channel capacities are analyzed     

基于移动参考节点的无线传感器时钟同步方法

现有对无线传感器网络节点中的时钟同步方法往往通过固定参考节点传递同步信息完成同步。对于固定参考节点通信范围外的节点,需要同步信息在节点间的多跳传输,这造成时间误差的累积以及节点多跳传输的能量损耗,从而影响同步的精度和网络能耗。为解决此问题,提出了基于移动参考节点和最优移动路径的时钟同步方法。首先,采用正六边形的蜂窝覆盖技术选取最优的时钟同步点。其次,结合最优覆盖和选址问题的数学模型,设计最短移动距离的路径。最后,提出了基于MAC层标记多个时间戳实现低能耗单跳同步的机制。与现有方法的实验对比表明,该方法提高了同步时间精度,并降低了通信能耗。     

CORD: contention resolution by delay lines

The implementation of optical packet-switched networks requires that the problems of resource contention, signalling and local and global synchronization be resolved. A possible optical solution to resource contention is based on the use of switching matrices suitably connected with optical delay lines. Signalling could be dealt with using subcarrier multiplexing of packet headers. Synchronization could take advantage of clock tone multiplexing techniques, digital processing for ultra-fast clock recovery, and new distributed techniques for global packet-slot alignment. To explore the practical feasibility and effectiveness of these key techniques, a consortium was formed among the University of Massachusetts, Stanford University, and GTE Laboratories. The consortium, funded by ARPA, has three main goals: investigating networking issues involved in optical contention resolution (University of Massachusetts), constructing an experimental contention-resolution optical (CRO) device (GTE Laboratories), and building a packet-switched optical network prototype employing a CRO and novel signaling/synchronization techniques (Stanford University). This paper describes the details of the project and provides an overview of the main results obtained so far     

Implementation mechanisms for packet switched voice conferencing

A distributed control mechanism for managing a packet-switched voice conference connection is presented. The principal concept introduced is the idea of viewing a conference connection as a logical ring of participants. Alternative methods for implementing voice conferencing on both broadcast and point-to-point networks are introduced, analyzed, and compared. Tradeoffs between the two methods with respect to station workload and maximum number of conference participants are discussed. Experimental implementations on both a carrier-sense multi-access with collision detection (CSMA/CD) Ethernet and a token-ring ProNet are described. The mechanisms presented can be used as part of a packet-switched voice communications protocol that includes conferencing capabilities     

基于IEEE1588精确时间同步的无线传感器网

无线传感器网(WSN)正在从要求不高的应用向要求更高的应用演进。分布式实体和事件的协调需要时间同步。虽然,已开发了很多用于WSN的时间同步方法,但某些应用需要高精度时间同步。精确时间同步支持应用的各种扩展。IEEE 1588精确时间协议(PTP)提供在一个网络中,一种具亚微秒精度、标准的设备同步方法。本文研究了在无线传感器网上,使用IEEE 1588的精确时间同步。使用IEEE 1588的精确时间同步提供了WSN中异构系统间的兼容性。     

A novel self-routing address scheme for all-optical packet-switched networks with arbitrary topologies

Pure all-optical packet-switched networks in which both header processing and packet routing are carried out in the optical domain overcome the bandwidth bottlenecks of optoelectronic conversions and therefore are expected to meet the needs of next generation high speed networks. Due to the limited capabilities of available optical logic devices, realizations of pure all-optical packet-switched networks in the near future will likely employ routing schemes that minimize the complexity of routing control. In this paper, we propose a novel self-routing scheme that identifies the output ports of the nodes in a network instead of the nodes themselves. The proposed address scheme requires single bit processing only and is applicable to small to medium size pure all-optical packet-switched networks with arbitrary topologies. Unlike traditional self-routing schemes, multiple paths between two nodes can be defined. An hierarchical address structure can be used in the proposed routing scheme to shorten the address.     

Slot Synchronization of a WDM Packet-Switched Slotted Ring

In this paper, we present two different strategies of slot synchronization in wavelength-division-multiplexing (WDM) packet-switched slotted-ring networks. Emphasis is given to the architecture behind the WDM optical network demonstrator over rings (WONDER) project, which is based on tunable transmitters and fixed receivers. The WONDER experimental prototype is currently being developed at the laboratories of Politecnico di Torino. In the former strategy, a slot-synchronization signal is transmitted by the master station on a dedicated control wavelength; in the latter, slave nodes achieve slot synchronization aligning on data packets that are received from the master. The performance of both synchronization strategies, particularly in terms of packet-collision probability, was evaluated by simulation. The technique based on transmitting a timing signal on a dedicated control wavelength achieves better performance, although it is more expensive due to the need for an additional wavelength. However, the technique based on aligning data packets that are received from the master, despite attaining lower timing stability, still deserves further study, particularly if limiting the number of wavelengths and receivers is a major requirement. Some experimental results, which were measured on the WONDER prototype, are also shown. Measurement results, together with theoretical findings, demonstrate the good synchronization performance of the prototype.     

传输网定时同步和互联网时间同步

传输网的定时同步是电信网络的物理层需求，而互联网的时间同步则是通过应用层上网络时间协议(NTP)来实现，服务于互联网上的应用层需求。两者的网络结构、实现和功能均有很大不同。     

一种长时延网络中移动节点间的时间同步算法

长时延网络的同步对于提升网络传输效率,增加网络吞吐量具有重要意义。现有用于长时延网络典型时间同步协议有TSHL,Tri-Message等,这些同步协议都是针对传播时延保持稳定或者保持短时稳定的长时延网络,但在实际情况中,有时传播时延会发生变化,如节点间相对位移的变化,如何在这样的长时延网络中进行时间同步也是一个值得研究的问题,文中提出了一种运用于长时延网络中移动节点间的时间同步算法,利用节点间多次的信息交互计算出传播时延变化的速率,然后对时延变化进行估算来进行时间偏移的补偿以达到时间同步。     

略谈通信网时频同步技术演进趋势

根据ITU-T近期发布的通信同步技术标准建议书，纵观电信运营商对于同步网发展所做的努力，分析国内外厂商和研究单位的代表性新产品，尝试探讨通信同步网和网同步的演进趋势，归纳其特点是：为了迎接5G移动通信等新挑战，通信网时频同步性能指标在明显提升，尤其是高精度时间同步受到更大的重视，需要采用新技术改变传统同步方式，需要研制和运用新的同步设备和检测仪表，新的同步技术标准也彰显了中国在国际的引领作用和影响。