WDM网络动态组播业务共享保护算法

该文研究了WDM网络中动态组播业务的保护.为提高网络资源的利用率,降低连接请求阻塞率,和单播业务的共享保护方案类似,组播连接之间也可以共享保护波长.本文提出了一种动态组播业务共享保护算法,并对算法的性能进行了仿真,同时和组播业务专有保护算法进行了比较.仿真结果表明,共享保护算法比专有保护算法使用了更少的波长资源,具有更低的连接阻塞率.     

基于位置的双播机制在高速铁路越区切换中的应用

提出了一种适用于高速铁路环境的LTE越区切换方案,该方案利用列车移动轨迹的固定性和列车运行的规律性,采用了基于位置的双播机制。和传统采用双播机制的越区切换方案相比,该方案能够降低切换中断时间,最小化双播带来的额外网络开销。     

WDM-PON中基于码型动态切换的组播实现方案

提出了一种利用码型动态切换的机制来实现波分复用无源光网络中组播业务的传输.组播业务采用DPSK调制格式,下行单播业务采用动态切换的Manchester/NRZ调制格式.其中Manchester调制格式是由下行单播数据和同频的时钟信号通过电逻辑异或门产生.实验验证了同时传输5Gb/s下行点对点信号和1.25Gb/s组播信号的WDM-PON组播传输方案的可行性.     

一种适用于Ad Hoc K重组播网络的负载均衡路由算法

Ad Hoc网络是一个多跳的无基础设施网络,本文在分析Ad Hoc网络自身特点的基础上,引入了一种多组播业务并存的K重组播网络,这种网络相对传统的组播网络具有节省系统开销,降低能量消耗的优点.文中对K重组播网络中的节点连接度的不同变化情况进行了理论上的详细研究,并在此基础上设计了一种适用于K重组播网络的负载均衡路由算法.仿真结果表明该路由算法拥塞控制性能良好,并能显著提高组播业务的稳定性.本文提出的这种K重组播网络能够广泛的应用于许多实际通信场合.     

WDM网络中的光层组播保护

组播应用主要是一些带宽密集型的业务,而光网络又能够提供巨大的带宽.随着光通信技术的发展,在光层实现组播已经成为光网络研究的热点之一.主要讨论了在光层实现对组播业务的保护,对现有的保护方案进行了分类和比较研究,最后讨论了有待进一步研究的问题.     

Small Cell中移动性增强方案研究现状分析

小蜂窝网络是由比传统宏蜂窝基站发射功率更小的低功率节点形成的多层蜂窝网络。作为LTE-Advanced技术研究的重要内容之一,小蜂窝的发展越来越受到业界的关注。分析评估了移动性管理中多种移动状态估计(MSE)方案的性能指标,同时分析评估了蜂窝切换中所涉及的切换指令的保护方案性能以及蜂窝切换方案性能,最后对小蜂窝网络移动性管理面临的挑战和未来的研究方向做出总结。     

WDM网络动态组播业务管道失效保护

在光网络的建设中,为降低建设成本,多条链路往往经过同一条管道。在很多情况下,光纤链路的失效是由管道故障引起的,需要为网络的管道故障提供保护。该文研究了动态组播业务的单管道故障保护,给出了两种专有保护算法(SDP-DP和SDS-DP)和一种保护波长共享保护算法(SDS-SDP),并对各算法的连接阻塞率进行了仿真分析。仿真表明,在大部分情况下,由于SDS-SDP共享了连接请求之间的保护波长,SDS-SDP算法的连接阻塞率最低;而在低网络负载的情况下,SDP-DP算法有最低的连接阻塞率。     

移动视频业务的快速频道切换方案研究

提出了一种基于间插切换帧的移动视频业务快速频道切换方案,通过合理增加切换帧减少频道切换中的主要时间,即等待参考帧时间.然后对所提方案进行了性能分析和验证,仿真结果表明该方案可有效减少移动视频业务的频道切换时间.     

WDM光网络中基于链路的动态组播共享保护算法

针对WDM光网络中单链路失效的情况,提出了一种基于链路的保护动态组播业务的优化共享保护算法(Link-based optimized shared-protection algorithm for multicast sessions,LB-OSPM).该算法在对工作树任意光纤链路失效情况寻找保护路径时,允许组播内不同保护路径共享预留波长资源,同时通过引入预留波长使用情况矩阵和波长预留矩阵记录预留波长资源的使用情况,实现了不发生冲突的不同组播的保护链路间共享预留波长资源.研究采用欧洲光网络(European Optical Network,EON)的拓扑对不同波长资源配置和网络负载情况下LB-OSPM算法的网络连接阻塞率做了仿真.结果表明,通过引入共享机制,LB-OSPM算法在对单链路失效保证100％恢复率的同时可以获得更低的连接阻塞率,提高了波长资源利用效率.     

WDM格型光网络中的动态组播共享保护算法

该文针对WDM格型网络中单链路失效的情况,提出了一种保护动态组播业务的基于路径的优化共享保护(PB-OSPM)算法。该算法在基于最优路径对的共享不相交路径(OPP-SDP)算法的基础上,通过引入保护波长使用情况矩阵和波长预留矩阵记录预留波长资源的使用情况,允许不发生冲突的不同组播的保护路径间共享预留波长资源。研究采用欧洲光网络(EON)的拓扑对PB-OSPM算法和OPP-SDP算法在增性网络负载情况下的网络冗余度和同波长资源配置和网络负载情况下动态网络负载的网络连接阻塞率做了仿真。结果表明,相同条件下,PB-OSPM算法比OPP-SDP算法有更低的连接阻塞率。组播业务间波长资源的共享是提高波长资源利用率的有效方法。     

Dynamic multicast sharing protection algorithm based on fuzzy game in multi-domain optical network

Aiming at the problem of dynamic multicast service protection in multi-domain optical network, this paper proposes a dynamic multicast sharing protection algorithm based on fuzzy game in multi-domain optical network. The algorithm uses the minimum cost spanning tree strategy and fuzzy game theory. First, it virtualizes two planes to calculate the multicast tree and the multicast protection tree respectively. Then, it performs a fuzzy game to form a cooperative alliance to optimize the path composition of each multicast tree. Finally, it generates a pair of optimal multicast work tree and multicast protection tree for dynamic multicast services. The time complexity of the algorithm is O(k3m2n), where n represents the number of nodes in the networks, k represents the number of dynamic multicast requests, and m represents the number of destination nodes for each multicast request. The experimental results show that the proposed algorithm reduces significantly the blocking rate of dynamic multicast services, and improves the utilization of optical network resources within a certain number of dynamic multicast request ranges.     

Achieving inter-session fairness for layered video multicast

The Internet is increasingly used to deliver multimedia services. Since there are heterogeneous receivers and changing network conditions, it has been proposed to use adaptive rate control techniques such as layered video multicast to adjust the video traffic according to the available Internet resources. A problem of layered video multicast is that it is unable to provide fair bandwidth sharing between competing video sessions. We propose two schemes, layered video multicast with congestion sensitivity and adaptive join-timer (LVMCA) and layered video multicast with priority dropping (LVMPD), to achieve inter-session fairness for layered video multicast. Receiver-driven layered multicast (RLM), layer-based congestion sensitivity, LVMCA, and LVMPD are simulated and compared. Results show both proposed schemes, especially LVMPD, are fairer and have shorter convergence time than the other two schemes.     

Designs of high-performance multicast scheduling mechanisms in WDM networks

In this article, we propose three multicast scheduling mechanisms, lookback queue access, lookback ratio access, and double check head access, for the employment in the single-star Wavelength Division Multiplexing optical network. Each of the proposed scheduling schemes consists of two phases and is executed in real time. In general, the first phase is to search for a candidate multicast packet that can be sent, without partition, to all of its intended recipients. If phase 1 fails, the second phase is then activated to partition a multicast packet into multiple transmissions in accordance with specific criteria of each individual mechanism. These algorithms are designed to mitigate the head-of-line blocking effect, while at the same time achieving excellent network throughput levels and delay performance via the partitioning procedure. Performance results reveal the distinct features of each mechanism under various scenarios. For a wider range of networking environments, we further propose an interconnected dual-star structure and enhanced multicast scheduling algorithms. These enhanced schemes aim to exploit the inter-data channels efficiently and utilize the wavelength reuse property of the intra-data channels properly. Performance results have demonstrated the merits of deploying the proposed multicast algorithms in such a dual-star structure.     

移动IP网络中的组播技术研究

主要讨论了基于移动IP网下的组播技术。在给出了基本的两种移动组播机制：即远程签署RS和双向隧道BT的基础上，重点分析了RBMoM协议，即基于范围的移动组播协议，同时比较了三者的优缺点。最后给出RBMoM协议的实现流程图。     

Efficient wireless multicast retransmission using network coding

In wireless multicast,network coding has recently attracted attentions as a substantial improvement to packet retransmission schemes.However,the problem of finding the optimal network code which minimizes the retransmissions is hard to solve or approximate.This paper presents two schemes to reduce the number of retransmissions for reliable multicast efficiently.One is retransmission using network coding based on improved Vandermonde matrix(VRNC),the other is retransmission using network coding based on adaptive improved Vandermonde matrix(AVRNC).Using VRNC scheme the sender selects the packets all receivers have lost and encodes them with improved Vandermonde matrix;when receivers receive enough encoded retransmission packets,all the lost packets can be recovered.With AVRNC scheme,the sender can obtain the recovery information from all the receivers after sending out per retransmission packet,and then the improved Vandermonde matrix can be updated,thus reducing the complexity of encoding and decoding.Our proposed schemes can achieve the theoretical lower bound assuming retransmission packets lossless,and approach the theoretical lower bound considering retransmission packets loss.Simulation results show that the proposed algorithms can efficiently reduce the number of retransmissions,thus improving transmission efficiency.     

Optical multicast provisioning with differentiated leaf availability guarantee in WDM networks

As multicast applications become more and more popular, implementing multicast in the optical domain has attracted increased attention due to its more efficient bandwidth usage. And also these services have quality-of-service requirements. In this article, the problem of cost-effective optical multicast provisioning to satisfy the differentiated leaf availability requirements is formally stated. A Mixed Integer Linear Program formulation is proposed for provisioning dedicated light-tree protection with differentiated leaf availability guarantee. The algorithm is so complex and infeasible that we also propose a feasible two-step approximate approach to solve the problem. Different from the previous schemes, our scheme finds out the primary light-trees and backup paths for destination nodes whose availability is not satisfied. Because of taking the different leaf availability requirements into account, the proposed algorithm obtains a more efficient feasible solution requiring less network resources.     

A study of multicast congestion control for UMTS

In this paper, we study the applicability of multicast congestion control over universal mobile telecommunications system (UMTS) networks. We analyze two well‐known multicast congestion control schemes for fixed networks, namely TCP‐friendly multicast congestion control and pragmatic general multicast congestion control. We investigate their behavior when they are employed in UMTS networks and we analyze the problems arose when these mechanisms are applied over the wireless links of the UMTS terrestrial radio‐access network. Additionally, we propose necessary improvements to these legacy schemes and explain the necessity of these modifications. The proposed schemes are implemented in the ns‐2 network simulator and are evaluated under various network conditions and topologies. Finally, we measure the performance of the proposed modified schemes and compare them with the corresponding legacy mechanisms. Copyright © 2009 John Wiley & Sons, Ltd.     

WDM PON中新型组播技术的研究

实现有效的组播传输是WDM PON实用化的关键技术之一,介绍了我们提出并实验验证了其可行性的几种WDM PON新型组播模式,为WDM PON技术的进一步发展和实际应用提供了参考与可选的业务组播方案.