用于ASON中的光交叉连接设备

光交叉连接(OXC)技术是光节点的关键技术,OXC是自动交换光网络(ASON)的核心,为此阐述了ASON的基本概念和特点,以及OXC的结构和工作原理,讨论了目前实现智能OXC的关键技术:智能光MEMS(微电子机械系统)技术和通用多协议标签交换技术.     

一种星载CICQ交换机单组播分组调度算法

以缓解联合输入交叉队列(CICQ)交换机分组调度中的组播HOL Blocking问题为目标,同时对因GEO信道问题传输失败而需要重传的分组进行补偿,提出一种新的单组播混合调度算法,即缓解组播头分组阻塞算法RMHB。该算法在交换机尽量工作于Work-Conserving的前提下,尽量缓解组播队列头分组对次分组的阻塞,在单组播分组裁决中,将分组在信道中重传的次数作为考虑的首要因素。目前尚未见到CICQ结构中在考虑GEO卫星信道状态的情况下,进行单组播混合业务分组调度的方法。     

光开关及其在全光网中的应用

光开关是完成全光交换的核心器件 ,光开关的研究日益成为全光通信领域关注的焦点。从光开关的性能指标开始系统介绍了光开关的类型 ,深入探讨了光开关构成的全光交换机的结构原理。随着数据网络的迅速发展 ,光开关将在全光网络中得到广泛的应用     

Scheduling Combined Unicast and Multicast Traffic in Broadcast WDM Networks

This paper studies the performance of various strategies for scheduling a combined load of unicast and multicast traffic in a broadcast WDM network. The performance measure of interest is schedule length, which directly affects both aggregate network throughput and average packet delay. Three different scheduling strategies are presented, namely: separate scheduling of unicast and multicast traffic, treating multicast traffic as a number of unicast messages, and treating unicast traffic as multicasts of size one. A lower bound on the schedule length for each strategy is first obtained. Subsequently, the strategies are compared against each other using extensive simulation experiments in order to establish the regions of operation, in terms of a number of relevant system parameters, for which each strategy performs best. Our main conclusions are as follows. Multicast traffic can be treated as unicast traffic, by replicating all multicast packets, under very limited circumstances. On the other hand, treating unicast traffic as a special case of multicast traffic with a group of size 1, produces short schedules in most cases. Alternatively, scheduling and transmitting each traffic component separately is also a good choice.     

组播技术及其在光层的实现

带宽密集型的多媒体应用对现有网络提出了新的要求,组播技术有助于解决其在网络带宽和服务质量方面的问题,而在光层实现组播具有更简单、高效的特点.然而,光层组播由于光缓存、光分束和光波长变换等光器件的限制,呈现出和IP层组播不同的特点.对IP层和光层组播进行了讨论,分析了光层组播模型,并对稀疏光分束和稀疏波长变换的光网络组播路由提出了重路由到源和重路由到相关节点两种重路由方式.     

Efficient QoS Partition and Routing of Unicast and Multicast

In this paper, we study problems related to supporting unicast and multicast connections with quality of service (QoS) requirements. We investigate the problem of optimal routing and resource allocation in the context of performance dependent costs. In this context, each network element can offer several QoS guarantees, each associated with a different cost. This is a natural extension to the commonly used bi-criteria model, where each link is associated with a single delay and a single cost. This framework is simple yet strong enough to model many practical interesting networking problems. An important problems in this framework is finding a good path for a connection that minimizes the cost while retaining the end-to-end delay requirement. Once such a path (or a tree, in the multicast case) is found, one needs to partition the end-to-end QoS requirements among the links of the path (tree). We consider the case of general integer cost functions (where delays and cost are integers). As the related problem is NP complete, we concentrate on finding efficient epsiv-approximation solutions. We improve on recent previous results by Erguumln Lorenz and Orda, and Raz and Shavitt, both in terms of generality as well as in terms of complexity of the solution. In particular, we present novel approximation techniques that yield the best known complexity for the unicast QoS routing problem, and the first approximation algorithm for the QoS partition problem on trees, both for the centralized and distributed cases     

An Optical Wavelength-Routed Multicast Packet Switch Based on Multitimeslot Multiwavelength Conversion

This letter presents a new scheme to realize multicast operation in a wavelength-routed optical packet switch by adding multicast modules. The proposed multicasting scheme is based on multitimeslot multiwavelength conversion in conjunction with wavelength selection to resolve the problem of output contention.      

Fairness and Dynamic Flow Control in Both Unicast and Multicast Architecture Networks

With the development of multicast service in the Internet, much attention has been drawn to multicast congestion control and analysis. Multicast traffic poses new challenges to the design of Internet congestion control protocols and system stability analysis. The rate control problem of feedback-based sessions on the coexistence of both unicast and multirate multicast traffic architecture networks is focused upon in this paper. First, a fairness problem is discussed in detail, and a reasonable consumption strategy is proposed. In the reasonable consumption strategy, scaling functions are adaptively adjusted based on a relationship between the session rates. Second, contraposing the case that available link capacities are changing with time for these feedback-based unicast and multicast sessions, stability analysis of a closed-loop rate control system under the modified rate mechanism is made based on Lyapunov stable theory. Finally, the simulations illustrate the effectiveness and goodness of the reasonable consumption strategy     

A Unified Framework for Multipath Routing for Unicast and Multicast Traffic

We study the problem of load balancing the traffic from a set of unicast and multicast sessions. The problem is formulated as an optimization problem. However, we assume that the gradient of the network cost function is not available and needs to be estimated. Multiple paths are provided between a source and a destination using application-layer overlay. We propose a novel algorithm that is based on what is known as simultaneous perturbation stochastic approximation and utilizes only noisy measurements collected and reported to the sources, using an overlay architecture.We consider three network models that reflect different sets of assumptions regarding multicast capabilities of the network. Using an analytical model we first prove the almost sure convergence of the algorithm to a corresponding optimal solution under each network model considered in this paper with decreasing step sizes. Then, we establish the weak convergence (or convergence in distribution) with a fixed step size. In addition, we investigate the benefits acquired from implementing additional multicast capabilities by studying the relative performance of our algorithm under the three network models.      

Adaptive Transmission Scheme for Mixed Multicast and Unicast Traffic in Cellular Systems

Wireless communication systems have been developed to support users' various requirements. Multicast and unicast transmission schemes are proposed for various types of services. The multicast transmission is known as an efficient method for group-data transmission. The data rate for multicast transmission depends on the instantaneous worst channel user. On the other hand, unicast transmission exploits wireless channel variation and achieves a multiuser diversity gain. In this paper, we evaluate and compare the system performance of multicast and unicast transmission schemes in terms of system capacity, worst average channel user's capacity, and outage probability for varying cell environments. We also propose a novel hybrid scheduling scheme for mixed multicast and unicast traffic services and compare the proposed scheme with the conventional scheme.      

Optimal Time Slot Assignment Algorithm for Combined Unicast and Multicast Packets

This paper considers a packet‐scheduling algorithm for a given combined traffic of unicast and multicast data packets and proposes a hybrid router with several dedicated buses for multicast traffic. Our objective is to develop a scheduling algorithm that minimizes schedule length for the given traffic in the hybrid router. We derive a lower bound and develop an optimal solution algorithm for the hybrid router.     

以太网交换机中组播技术的实现

目前各种基于宽带的多媒体应用层出不穷，这就迫切需要一种新的数据传播技术即组播技术的支持，最大效率地利用现有有限的网络资源。首先介绍了组播技术的相关基础知识，然后重点描述了流行的组播协议IGMP协议，基于此作者结合自己的课题，以一交换芯片为例，讨论了如何在二层交换机中实现组播功能。     

一种基于OFDMA的组播单播联合自适应调度算法

 面向未来的大型多媒体组播应用环境,在IEEE 802.16业务分类的基础上,提出了名为VARTUL的业务分类及制约关系,在此基础上,研制了基于OFDMA的VARTUL节能调度算法,力求终端休眠时间最长,切换次数最少.算法中组播和单播共存,在制约前提下支持大量级用户的自由订阅,从而支持广播电视业务与数据业务的融合与运营.实验仿真表明,VARTUL算法能自适应上下行流量变化和各业务流量分布,支持各种业务组合,确保用户体验,并节约终端能量.     

Coordinated Multicast/Unicast Transmission on 5G: A Novel Approach for Linear Broadcasting

Wireless Personal Communications - The underwate communication is of great interest of research for many researchers because of increased dealings of human beings with world exists underwater....     

一种支持单播与组播混合业务的高速Crossbar调度算法

当前在高速crossbar中支持单、组播混合业务调度的实用算法一般采用请求-许可-接受的处理流程(例如ESLIP算法)。研究发现,该类算法中存在单、组播许可相互阻塞现象,造成调度效率降低。从实用性出发,该文提出了一种新的支持单、组播混合业务的调度算法ERGRR(Extended Request-Grant-based Round- Robin),通过简化调度处理流程,克服了许可阻塞现象,提高了系统吞吐量、时延等性能。仿真结果表明,在单、组播混合业务流下,ERGRR算法吞吐量、时延等性能优于ESLIP算法。另外,ERGRR算法具有更好的公平性以及更加易于硬件实现。     

Multilink Solution for Seamless Transition Between Multicast and Unicast Areas in 5G Core Network

Wireless Personal Communications - The exponential growth in technology observed over the past decade has introduced newer ways to exploit network and cyber-physical system-related vulnerabilities....     

硅基光开关及阵列研究进展北大核心

随着网络传输数据的爆炸式增长,传统集成电路芯片面临着难以进一步提升交换速率及继续扩大容量等挑战。相较于传统电子芯片,硅基光子器件具有交换速度快、功耗低、带宽大和与CMOS工艺兼容性好等优点,可满足下一代全光交换网络、数据中心和高性能计算光互连的迫切需求,被视为在后摩尔时代突破芯片容量最具前途的解决方案,受到日益广泛关注。文章介绍了硅基光子芯片中光开关单元及阵列的技术原理和发展现状,重点论述了MZI型、MRR型开关单元,以及常见阵列拓扑结构,介绍了近年来大规模光开关阵列的国内外研究进展,讨论了未来硅基光开关及阵列研究中面临的主要问题和解决方法。     

All-Optical Multicast Switch Employing Raman-Assisted FWM in Dispersion-Shifted Fiber

We demonstrate an all-optical multicast switch with the capability to select five reconfigurable channel groups with six output multicast channels using three control wavelengths at 10 Gb/s using Raman-assisted four-wave mixing in dispersion-shifted fiber. All the output channels comply with the 100 GHz (i.e., 0.8 nm) spaced International Telecommunication Union (ITU) grid.     

保证100%吞吐率的两级组播交换结构

在路由器或交换机的交换结构中实现组播是提高组播应用速度的重要途径之一。传统的交叉开关结构(crossbar)组播调度方案有两种缺陷,一种是性能较低,另一种是实现的复杂度太高,无法满足高速交换的需要。该文提出了一个新的基于交叉开关的两级组播交换结构(TSMS),第1级是组播到单播的交换结构,第2级是联合输入和输出排队(CIOQ)交换,并为该结构设计了合适的最大扇出排队(FCN)优先-均匀分配中间缓存调度算法(LFCNF-UMBA)。理论分析和仿真实验都显示在该结构中,加速比低于22/(N+1)倍时吞吐率不可能实现100%;而采用LFCNF-UMBA调度算法,2倍加速比就可保证在任意允许(admissible)组播的吞吐率达到100%。     

光通信网络中的光开关技术

对光开关的类型、特性及研究现状进行了讨论,并重点对MEMS光开关及其工艺技术进行了分析,指出MEMS是未来光开关技术的一个重要发展方向。