有线电视网络中数字电视技术的应用研究

文本主要针对有线电视网络中数字电视技术的应用展开深入研究,先阐述了数字电视技术在有线电视网络应用中的优势,如数字电视技术信号传输稳定、数字电视技术具有一定的操作性、数字电视图像画面清晰化等等,然后结合应用电视技术时遵循的要点,提出了几点切实可行的应用措施,如数字机顶盒的应用、网络电视机的应用等等,通过以上措施,促进有线...     

异常流量疏导技术的研究及其在电信IP网的应用

本文研究和分析了异常流量防范技术的现状,通过实验和测试验证异常流量疏导技术和方案,并提出了在现行技术和产品的情况下应用异常流量疏导的技术方案,以缓解在电信IP网上日益严重的异常流量问题.     

HFC有线电视网络技术研究

随着信息技术的发展,各地广电运营商纷纷加入了对有线电视网双向化改造的大军中,HFC有线电视网成为目前最为普及的电视网络,在数字化、双向化的信号传输途中,进行科学合理的维护和管理是保障电视用户正常使用的关键之一。文章以光纤同轴电缆混合网络-HFC宽带接入网的拓扑结构、频率规划及双向传输的实现方式等为重点,综合介绍了有线电视网络目前实施的系统组成。     

有线电视网络中数字电视技术的应用

在很长一段时间内,国内的有线电视所使用的都是模拟电视技术。但是,随着社会的快速发展,人们的生活质量也在不断提高,模拟电视技术的应用已经无法满足人们的精神需求。如今,科学技术迅猛发展,有线电视也进行了改革和调整,数字电视技术逐渐取代了模拟电视技术,而且应用范围正在不断扩大。数字电视已经进入千家万户,多数住宅都安装了数字电视,更好地满足了人们的精神需求。     

有线电视网络光纤到户技术应用

本文介绍了采用RF混合光纤到户进行有线电视网络升级改造的方案,阐述了有线电视网络升级改造应该从特定的场景出发,充分利用网络存量资源,选择合理的光纤到户方案,提高网络的综合性能。     

有线电视网络中数字电视技术的应用研究

本文针对数字电视技术,通过分析其含义、分类、应用优势及注重要点,提出数字技术在有线电视网络中的具体应用,并结合当前实际提出发展状态,其目的在于提高电视信号稳定度和画面清晰度,有效解决以往出现的卡屏和信号中断等问题,最终提升电视节目播放流畅性和观众满意度,同时促进有线电视网络稳定地发展.     

有线电视网络中UPS的应用和维护

1　有线电视网络ＵＰＳ的选用ＵＰＳ电源按其工作方式可分两种 ,一种是离线式(即后备式 ) ,其输出是方波 ;另一种是在线式 ,其输出为正弦波。离线式ＵＰＳ在市电供电正常时 ,机内的逆变处于停止等待状态 ,由市电向负载供电。停电时 ,由蓄电池直接经逆变器向负载提供稳压稳频的交流电 ,其切换存在一个转换时间 ,一般只有几毫秒 ,对于要求不高的领域比较适合 ,价格便宜。方波输出的ＵＰＳ电源带负载能力差 ,仅为额定负载的 4 0 %～ 6 0 % ,不能带电感性负载。在线式ＵＰＳ电源逆变输出是正弦波 ,外部提供的交流电通过在线ＵＰＳ变为直流 ,直流…     

WDM光网络中动态流量的疏导

流量疏导是当今光网络研究中的一个前沿和热点问题,在波分复用(WDM)光网络中使用流量疏导技术能有效降低网络的成本,减少网络节点中业务信息的处理量.文章讨论了动态流量疏导的意义及其分类,分析了关于在各种网络结构中动态流量疏导的研究近况,最后对今后的发展方向做了一番展望.     

有线电视网络发展和几种双向接入技术的比较

多业务的导入，尤其是大带宽需求的交互视频业务的要求，使得运营商需要对目前的单向或小流量的双向网络进行改造，目前双向接入技术比较多，下面笔者对4类主要的接人技术做具体分析和比较（具体比较见表1）。     

支持多优先级QoS的业务量疏导算法

针对当前业务量疏导研究中很少涉及的QoS约束的问题,提出并研究了一种支持多优先级QoS的业务量疏导算法（Differentiated Traffic Grooming Algorithm,DTGA）,该算法综合考虑了对不同等级业务QoS和网络资源利用率的优化。与目前实用的WDM光网络业务量疏导算法的性能仿真对比表明,DTGA能有效地降低高服务等级需求业务的阻塞率和节省网络资源。     

Heuristic Algorithms for Grooming of Arbitrary Traffic in WDM Ring Networks

In a wavelength division multiplexing (WDM) network, sub-wavelength traffic streams can be elaborately arranged in wavelength channels to minimize the number of required electronic end systems, known as the traffic grooming problem. In this paper, a modified genetic algorithm without crossover operation is proposed to solve the problem using a permutation-based chromosome representation and using a selection strategy of reproducing the best chromosomes, thereby minimizing the number of electronic devices and requiring less wavelengths. Then, three methods are developed to improve the performance of the algorithm and a hill-climbing algorithm is proposed for the same purpose. Computer simulations were performed with plenty of randomly generated traffic patterns in unidirectional rings. The results show that these methods can improve the algorithm considerably. The relationships between the minimized network cost and the number of nodes are also presented.     

Combining GA with Splitting Methods for Rearrangeably Nonblocking Grooming of Dynamic Traffic in SONET Ring Networks

SONET/WDM rings are widely deployed in today’s networks. To reduce the total cost of such a network, an efficient way is using the traffic grooming technique to minimize the number of add/drop multiplexers (ADMs) on the ring. Since traffic often changes frequently, the problem of supporting dynamic traffic patterns with minimum number of ADMs and wavelengths becomes incresingly important, which is referred to as grooming of dynamic traffic. In this paper, we will deal with rearrangeably nonblocking grooming of arbitrary dynamic traffic in such ring networks. We will discuss in detail the benefit of splitting methods to such a grooming way and apply them to this kind of grooming. A novel genetic algorithm (GA) approach with a hierarchical chromosome structure for each individual is proposed in combination with splitting methods to address such grooming problems. Computer simulation results under different conditions show that our algorithm is efficient in reducing both the numbers of ADMs and wavelengths.     

Design and Performance Evaluation of Traffic Grooming Algorithms in WDM Multi-Ring Networks

In this paper, we propose novel traffic grooming algorithms to reduce the cost of the entire system in WDM multi-ring networks. In order to achieve this goal, it is important to construct a virtual topology and groom the traffic in these networks. We consider four kinds of virtual topologies of WDM multi-ring networks according to the way in which traffic is transmitted among rings. Accordingly, we design four kinds of traffic grooming (TG) algorithms depending on the considered virtual topologies: mixed (MTG), partially mixed (PMTG), separate (STG), and independent (ITG) traffic grooming algorithms. Each algorithm consists of a separation, a connection-ring construction, and a grooming procedure. In the separation procedure, all traffic connections are classified into intra and inter-connections. The connection-ring construction procedure makes full connection-rings from traffic connections. The grooming procedure groups connection-rings onto a wavelength in order to reduce the number of SONET add/drop multiplexers (SADMs) and wavelengths and to improve the utilization of network resources. To analyze the performance of each algorithm, a circular multi-ring architecture with uniform traffic is considered. The simulation results show that ITG and PMTG are more efficient in terms of wavelengths. STG and PMTG require a smaller number of SADMs.     

Improved Approaches for Cost-Effective Traffic Grooming in WDM Ring Networks: Uniform-Traffic Case*

To fully utilize the capabilities of a SONET/ADM network, traffic grooming is needed to multiplex a number of lower-rate traffic streams into a higher-rate stream, and vice versa. Although the capacity of a SONET ring network can be upgraded by operating it over multiple wavelengths, the corresponding network design may be costly if it employs a large number of ADMs. A cost-effective design attempts to minimize the total number of ADMs used in the network while carrying the offered traffic. We introduce and evaluate the performance characteristics of two new traffic-grooming approaches for WDM ring networks, called single-hop and multihop. Our single-hop implementation uses the simulated-annealing heuristic. After placing all the traffic on virtual circles, we group the circles in order to reduce the number of ADMs in the network. Our multihop implementation places an ADM at each node based on the requested traffic in the traffic-demand matrix; then, it tries to groom the wavelengths which can be groomed. We select one of the nodes to be the hub node which has an ADM for each wavelength. The hub node, therefore, can bridge traffic between all of the wavelengths. Each algorithm is specified and illustrated by a simple example. Our results demonstrate that it is beneficial to use a single-hop approach based on simulated annealing for a small grooming ratio, but for a large grooming ratio and node number, we advocate the use of the multihop approach.     

一种新型动态流量疏导策略

在WDM光网络中业务流量疏导能够有效地降低网络建设成本.为了疏导网络中的动态业务,提出动态业务流量的可重构疏导方案,并给出相应快速在线算法.此算法通过动态调整网络的虚拟拓扑结构,可使网络适应各种动态业务.计算机模拟结果表明,该算法能得到较优的疏导结果.     

基于HFC下的有线宽带网

主要介绍利用HFC网（广电光纤同轴混合网）开展有线宽带网络，它与电信宽带相比具有许多优势。还介绍了有线宽带网的原理。组成及功能。     

业务疏导技术在WDM网络及OPS网络中的应用

在波分复用(WDM)光网络中,可使用业务疏导(Traffic Grooming)技术来提高网络性能,降低网络成本.详细阐述了WDM光网络中业务疏导的基本概念及主要目标,并对国内外研究现状进行了总结.最后介绍了OPS光交换网络中使用的业务疏导技术.     

Dynamic Grooming Algorithms for Survivable WDM Mesh Networks

Within a WDM grooming mesh network and under the constraints of the number of transceivers per node and wavelength continuity, we propose a novel dynamic grooming graph which models the number of transceivers per node in addition to the usage of wavelength and bandwidth resources. Based on the grooming graph, we first propose a dynamic traffic-grooming algorithm called integrated grooming algorithm (IGA). And we also propose two dynamic survivable traffic-grooming algorithms, which are called protection per lightpath traffic-grooming algorithm (PPL) and protection per connection traffic-grooming algorithm (PPC). These algorithms are evaluated via simulations.     

NGN业务在HFC网络上的应用

提出了NGN业务对IP承载网络的要求．探讨了NGN语音业务在HFC网络上的组网模式以及在HFC网络上的QoS保证。