3G与无线局域网联合组网及漫游技术分析

简要介绍了第三代移动通信网(3G)和无线局域网(WLAN)的发展现状、使用情况、各自的特点以及组网方式和漫游方式,针对两者在有效数据传输率、使用频段、覆盖范围、漫游策略和资费等方面的适用范围和互补性,在详细分析3G和WLAN联合组网漫游所具有优势的基础上,阐述了3G与WLAN联合组网和漫游的可行性,提出了一种两者联合组网和数据业务无缝漫游的实现方案,得出3G和WLAN联合组网在未来具有广泛应用前景的结论。     

Is multilayer networking feasible?

IP traffic has been growing every year, bringing the need for deploying an IP backbone interconnected by links provided by the transport network. Thus, network operators have had traditionally divided their core network in two, the IP network and the transport network. Network planning and engineering tasks have been performed independently in both domains. Traditionally, the transport network has been quite inflexible, and changes have often required a long time to occur. However, recent developments in the control plane allow flexibility in the transport network, making it possible to set up and tear down circuits on demand. In this light, multilayer traffic engineering has been proposed to jointly manage both IP and transport layers, with the aim of optimizing the use of resources. This paper aims to describe the rationale behind multilayer traffic engineering, demonstrate its feasibility and quantify its advantages in terms of cost effectiveness. Also, this work takes a look at the different choices in performing the multilayer operation, in terms of control plane implementation and equipment integration. Finally, the paper presents a report on multilayer traffic engineer experimentation which proves its feasibility and show a preliminary techno-economic case study of the multilayer operation.     

Lightpath Versus Semi-Lightpath: Some Studies on Optimal Routing in WDM Optical Networks

This paper deals with the problem of optimal dynamic routing in WDM optical networks with wavelength-changing facilities available at some of the nodes. The route may be either a lightpath (i.e., wavelength continuous channel) or a semi-lightpath (i.e., wavelength-converted channel). We attempt to estimate in this work the gain in blocking probability, when we move from lightpath routing to semi-lightpath routing, keeping the number of wavelengths fixed, in a given circuit switched network. We ensure optimal (minimum cost) routing in both the cases by using the algorithm of Banerjee et al. [7,8] (called Algorithm-I in this paper) for lightpaths and that of Chlamtac et al. [6] (called Algorithm-II) for semi-lightpaths. Our results indicate that, for both the algorithms, the blocking probability (P_B), as expected, increases with network load. At light load, P_B for Algorithm-I is always larger than that for Algorithm-II. But the rate of increase in P_B is slightly higher in case of Algorithm-II, so that there is a crossover point where P_B for Algorithm-II exceeds P_B for Algorithm-I. This probably happens due to the irregularities in the semi-lightpaths at heavy loads when almost all routes are exhausted in the network. However, since this crossover phenomenon occurs at a very congested status of the network, it has little significance over the real life operation of a network. It only suffices to indicate that, under heavy load, both the algorithms are equally insufficient, and conversion does not improve the situation as might have been expected intuitively.     

Virtualizing Network and Service Functions： Impact on ICT Transformation and Standardization

Virtualization of network/service functions means time sharing network/service（and affiliated）resources in a hyper speed manner.The concept of time sharing was popularized in the 1970s with mainframe computing.The same concept has recently resurfaced under the guise of cloud computing and virtualized computing.Although cloud computing was originally used in IT for server virtualization,the ICT industry is taking a new look at virtualization.This paradigm shift is shaking up the computing,storage,networking,and ser vice industries.The hope is that virtualizing and automating configuration and service management/orchestration will save both capes and opex for network transformation.A complimentary trend is the separation（over an open interface）of control and transmission.This is commonly referred to as software defined networking（SDN）.This paper reviews trends in network/service functions,efforts to standardize these functions,and required management and orchestration.     

光纤通信技术的发展趋势

文章首先简单地回顾了光纤通信近20年的历程,接着分别详细说明现代光纤通信技术中波分多路系统、光纤放大器、新型单模光纤和组建光传送网等4个最突出项目的发展趋势。     

Transmission Range Effects on AODV Multicast Communication

As laptop computers begin to dominate the marketplace, wireless adapters with varying bandwidth and range capabilities are being developed by hardware vendors. To provide multihop communication between these computers, ad hoc mobile networking is receiving increasing research interest. While increasing a node's transmission range allows fewer hops between a source and destination and enhances overall network connectivity, it also increases the probability of collisions and reduces the effective bandwidth seen at individual nodes. To enable formation of multihop ad hoc networks, a routing protocol is needed to provide the communication and route finding capability in these networks. The Ad hoc On-Demand Distance Vector Routing protocol (AODV) has been designed to provide both unicast and multicast communication in ad hoc mobile networks. Because AODV uses broadcast to transmit multicast data packets between nodes, the transmission range plays a key role in determining the performance of AODV. This paper studies the effects of transmission range on AODV's multicast performance by examining the results achieved at varying transmission ranges and network configurations.     

MSC Pool组网与传统组网的位置更新比较

简要介绍了传统组网和MSC Pool的技术原理及组网方式;对比分析了这2种组网方式下的3种位置更新,即移动台的位置更新、用户跨MSC Pool的位置更新及周期性位置更新;说明了MSC Pool组网方式较传统组网方式因消除了池内跨局位置更新,从而更好地释放了HLR和MSC的处理能力,提高了通信网络的可靠性和可用性。     

基于对象Petri网的雷达组网系统建模仿真研究

建立了复杂环境下雷达网的OPDL模型,并以雷达网分布式目标检测分析为背景,运用所建立的雷达网OPDL模型进行了仿真实验。研究表明,基于OPDL的雷达组网系统建模仿真是一种分析、评价雷达网系统的有效途径。     

视频通信的现状及发展趋势

人们对视频通信业务的需求促进与其相关的网络、信息处理、网络接入等技术的发展,同时这些技术的不断发展也反过来促使视频通信业务的不断成熟。未来视频通信业务将会承载于有线可无线Internet上．同时其服务质量也将会满足商业化发展的需要。目前面临的挑战是视频通信应用中会涉及很多知识产权问题、家庭组网尚未形成明确的主流技术,此外还有安全问题和商业模式的建立等。但我国与其他许多国家处在同一起跑线上。存在着许多创新的机会和领域。     

基于概率的启发式ICN缓存内容放置方法

提出一种基于概率存储的启发式住处中心网络内容缓存方法（PCP）。主要思想是请求消息和数据消息在传输过程中统计必要信息,当数据消息返回时,沿途各缓存节点按照一定概率决策是否在本地缓存该内容。设计缓存概率时综合考虑内容热度和缓存放置收益,即内容热度越高,放置收益越大的内容被缓存的概率越高。实验结果表明,PCP在缓存服务率、缓存命中率、平均访问延迟率等方面,与现有方法相比具有显著优势,同时PCP开销较小。