网络办公网络扫描

现代化的办公环境与网络办公是分不开的,网络办公不仅为公司节省了办公费用,同时还提高了办公效率,也更加方便了忙碌的公司员工.人们通过公司的内部网,可以沟通工作事宜,开电话会议;E-mail替代打印的信件与公函,做到了无纸办公;用一台网络打印机进行网络打印,节省了办公设备的投资与办公面积.而以前作为图形图像行业专用的扫描仪也普及到了普通办公领域.扫描仪可以配合OCR文字识别软件,使文字输入变得轻而易举,也可以把千篇一律的文件变得更加生动、多姿多彩.     

下一代网络的网络管理系统

１前言宽带数据业务的爆炸式增长和一些新业务的出现促进了传输网的迅猛发展。在短短的几年时间内 ,传输网的容量由过去的１５５Ｍｂｉｔ／ｓ、６２２Ｍｂｉｔ／ｓ、２．５Ｇｂｉｔ／ｓ发展到现在的Ｔｂｉｔ／ｓ ,网络规模越来越大 ,网络拓扑也越来越复杂。网络管理系统作为网络的一个重要组成部分 ,负责监控全网设备 ,保证网络高效、安全、可靠地运行。为了提高服务质量和降低运维成本 ,网络运营商对网管提出了更多、更高的要求。２网管的发展趋势按照ＩＴＵ＿ＴＭ．３０１０的建议 ,网管应有５大管理功能 ,即故障管理、配置管理、计费管理…     

电源线网络与电话线网络

墙壁中就有一个计算机风格——只不过你不知道罢了。有两种新兴的网络方案可以使用已有的电源线或电话线在计算机之间传输数据,而且在你使用这些网络的同时,仍然可以通电话或使用搅拌器等家用电器。     

网络言论与网络舆论导向

作为第四媒体的互联网，网络言论起到了不可低估的作用，其最大的意义就是造成了一种开放的信息传播环境。在互联网网络传播中媒介对社会舆论的相对垄断被打破，信息传播途径的多样化促进了信息获取能力和言论表达的机会。互联网网络在促进言论开放的同时，网络言论的自由化也带来了一系列负面影响。本文拟对在开放环境下互联网网络言论的导向、规范和监督管理提出一些建议和思考。（文中网络指国际互联网络）     

优化网络结构调整网络等级

在电总的统一部署下，中国长途电话网从１９９７年１１月至１９９８年２月底，成功地完成了长途４级网向２级网的调整。北京作为业务领导局、方案制定局、网调牵头局，率先完成了这次网调任务。调整后的网络结构清晰，形成了新的组网格局，完成了全国３１个省、市、自治区...     

服务 扎根网络 超越网络

从2007年到2008年,国内电信运营商在网络宽带化、IP化上的速度不断加快,使得更丰富的多媒体业务成为了可能。 今年是摩托罗拉中国区宽带及移动网络事业部服务部总经理吴达光在摩托罗拉服务的第十五年,与摩托罗拉一起,他亲身体验了中国移动通信行业的连续数年快速发展。对如何“服务”电信业以及帮助电信业“服务”用户,他有着最为深切的体会。     

网络

华为近日宣布在业界首家推出基于宽带MCPA（多载波功放）技术的TD—SCDMA宽带RRU（射频拉远单元）。该产品与解决方案的推出．将进一步推动TD—SCDMA产业的成熟与大规模商用化进程．同时也意味着华为在射频宽带化领域取得重大突破。华为宽带RRU在不同频段的射频输出功率和载波等系统资源完全共享．可以恨据运营商的需要和用户发展来进行灵活配置．达到资源最大化利用,同时实现TD-SCDMA向TD-LTE的真正平滑演进。     

网络

上海贝尔TD-LTE试验网速率达80Mbit／s 本刊讯（记者 徐超）日前，上海贝尔宣布在中国移动TD—LTE试验网上实现了80Mbit／s的下载速率。据了解该TD—LTE网络峰值速率是在上下行共用的20MHz无线频段上实现的．此外，阿尔卡特朗讯还在北京顺义地区进行的TD-LTE外场测试中获得佳绩。     

iTCP: an intelligent TCP with neural network based end-to-end congestion control for ad-hoc multi-hop wireless mesh networks

Maintaining the performance of reliable transport protocols, such as transmission control protocol (TCP), over wireless mesh networks (WMNs) is a challenging problem due to the unique characteristics of data transmission over WMNs. The unique characteristics include multi-hop communication over lossy and non-deterministic wireless mediums, data transmission in the absence of a base station, similar traffic patterns over neighboring mesh nodes, etc. One of the reasons for the poor performance of conventional TCP variants over WMNs is that the congestion control mechanisms in conventional TCP variants do not explicitly account for these unique characteristics. To address this problem, this paper proposes a novel artificial intelligence based congestion control technique for reliable data transfer over WMNs. The synergy with artificial intelligence is established by exploiting a carefully designed neural network (NN) in the congestion control mechanism. We analyze the proposed NN based congestion control technique in detail and incorporate it into TCP to create a new variant that we name as intelligent TCP or iTCP. We evaluate the performance of iTCP using both ns-2 simulations and real testbed experiments. Our evaluation results demonstrate that our proposed congestion control technique exhibits a significant improvement in total network throughput and average energy consumption per transmitted bit compared to the congestion control techniques used in other TCP variants.     

Asymptotic Capacity of Infrastructure Wireless Mesh Networks

An infrastructure wireless mesh network (WMN) is a hierarchical network consisting of mesh clients, mesh routers and gateways. Mesh routers constitute a wireless mesh backbone, to which mesh clients are connected as a star topology, and gateways are chosen among mesh routers providing Internet access. In this paper, the throughput capacity of infrastructure WMNs is studied. For such a network with Nc randomly distributed mesh clients, Nr regularly placed mesh routers and Ng gateways, assuming that each mesh router can transmit at W bits/s, the per-client throughput capacity has been derived as a function of Nc , Nr , Ng and W . The result illustrates that, in order to achieve high capacity performance, the number of mesh routers and the number of gateways must be properly chosen. It also reveals that an infrastructure WMN can achieve the same asymptotic throughput capacity as that of a hybrid ad hoc network by choosing only a small number of mesh routers as gateways. This property makes WMNs a very promising solution for future wireless networking.     

The Optimization of Combination Scheme in Cooperative Spectrum Sensing Based on the Practical Reporting Frame Format

Wireless mesh networks (WMNs) are emerged as prominent solution to provide seamless connection to the internet. WMNs are typically used for providing broadband wireless internet access to a large number of users and networks. Guaranteeing the quality of service to end users with efficient resource utilization is a challenging issue in WMNs. To accomplish this, we propose a hybrid routing protocol for wireless mesh networks. It is a combination of intra cluster routing protocol (ICR) and inter cluster routing protocol for mesh networks (ICMR). Intra cluster routing protocol is intended to facilitate the communication between mesh clients within a same cluster and inter cluster routing protocol (ICMR) intended to facilitate the communication for mesh clients from different clusters. Intra cluster routing protocol is a proactive type of routing protocol and inter cluster routing protocol is a reactive type of routing protocol. The performance of the proposed protocol is analyzed and the results shown superior performance compared to baseline routing protocols in terms of throughput, end to end delay, packet delivery ratio and jitter.     

Applications of network coding to improve TCP performance over wireless mesh networks: a survey

There is growing interest in the use of wireless mesh network (WMN) as a last‐mile option for Internet access. Despite the many benefits of WMNs, the performance of Internet access may not be ideal. One of the main issues is the interaction of transmission control protocol (TCP) with the underlying network. The poor performance of TCP over multi‐hop networks is well‐documented, and extensive research exists, which addresses TCPs foible and enhance TCP performance for multi‐hop environments. This paper provides a thorough survey of TCP performance issues over WMNs and the available solutions to address these issues. Among the existing methods, we focused on network coding (NC) and the ways that TCP interacts with network coded systems. NC is a technique that encodes the received packets in each node before forwarding them towards the destination. The use of NC in the transport layer to address performance issues raised by wireless access is a recent research topic. This paper presents a detailed study of TCP interaction with NC. Some open research areas in this field are suggested. Copyright © 2012 John Wiley & Sons, Ltd.     

Mitigating the gateway bottleneck via transparent cooperative caching in wireless mesh networks

Wireless mesh networks (WMNs) have been proposed to provide cheap, easily deployable and robust Internet access. The dominant Internet-access traffic from clients causes a congestion bottleneck around the gateway, which can significantly limit the throughput of the WMN clients in accessing the Internet. In this paper, we present MeshCache, a transparent caching system for WMNs that exploits the locality in client Internet-access traffic to mitigate the bottleneck effect at the gateway, thereby improving client-perceived performance. MeshCache leverages the fact that a WMN typically spans a small geographic area and hence mesh routers are easily over-provisioned with CPU, memory, and disk storage, and extends the individual wireless mesh routers in a WMN with built-in content caching functionality. It then performs cooperative caching among the wireless mesh routers.We explore two architecture designs for MeshCache: (1) caching at every client access mesh router upon file download, and (2) caching at each mesh router along the route the Internet-access traffic travels, which requires breaking a single end-to-end transport connection into multiple single-hop transport connections along the route. We also leverage the abundant research results from cooperative web caching in the Internet in designing cache selection protocols for efficiently locating caches containing data objects for these two architectures. We further compare these two MeshCache designs with caching at the gateway router only.Through extensive simulations and evaluations using a prototype implementation on a testbed, we find that MeshCache can significantly improve the performance of client nodes in WMNs. In particular, our experiments with a Squid-based MeshCache implementation deployed on the MAP mesh network testbed with 15 routers show that compared to caching at the gateway only, the MeshCache architecture with hop-by-hop caching reduces the load at the gateway by 38%, improves the average client throughput by 170%, and increases the number of transfers that achieve a throughput greater than 1 Mbps by a factor of 3.     

无线网状网技术与应用

无线网状网(WMNs)由网状路由器节点和客户机节点组成,其中的网状路由器节点组成了无线网状网的网络骨干,其移动性很小。他们一起为无线网状网和其他常规无线网络的客户机节点提供网络的无线接入。WMNs技术结合了中心式控制的蜂窝网与分布式控制的无线自组织网的优点,可有效克服这两种技术的缺陷并显著提高无线网络的性能,已经成为下一代无线通信网络的研究热点之一。WMNs可为无线个域网、局域网、校园网、城域网的一系列应用提供高速无线宽带接入服务。虽然目前WMNs技术发展很快,但其协议栈各层仍存在许多有待研究的课题。首先简要介绍了无线网状网的结构与特点;随后重点分析了其主要的几个应用领域;最后探讨了WMNs各协议层的研究现状与关键技术,并分析了该技术存在的问题及未来的研究方向。     

Throughput Gateways-Congestion Trade-Off in Designing Multi-Radio Wireless Networks

In Wireless Mesh Networks (WMNs), traffic is mainly routed by WMN Backbone (WMNB) between the mesh clients and the Internet and goes through mesh gateways. Since almost all traffic has to pass through one of the MGs, the network may be unexpectedly congested at one or more of them, even if every mesh router provides enough throughput capacity. In this paper, we address the problem of congestion of gateways while designing WMNs. We propose a simultaneous optimization of three competing objectives, namely network deployment cost, interference between network channels and congestion of gateways while guaranteeing full coverage for mesh clients. We tailor a nature inspired meta-heuristic algorithm to solve the model whereby, several trade-off solutions are provided to the network planner to choose from. A comparative experimental study with different key parameter settings is conducted to evaluate the performance of the model.     

A Novel Gateway Selection Technique for Throughput Optimization in Configurable Wireless Mesh Networks

Wireless mesh networks (WMNs) have attracted much attention due to their low up-front cost, easy network deployment, stable topology, robustness, reliable coverage, and so forth. These advantages are suitable for the disaster recovery applications in disaster areas, where WMNs can be advantageously utilized to restore network collapse after the disaster. In this paper, based on a new network infrastructure for WMNs, to guarantee high network performance, we focus on the issue of throughput optimization to improve the performance for WMNs. Owing to selecting different mesh router (MR) as the gateway will lead to different network throughput capacity, we propose a novel gateway selection technique to rapidly select the optimal MR as the gateway, in order to maximize the network throughput. In addition, we take into account the traffic distribution for the MR to eliminate traffic congestion in our method. The performance of our proposed method is evaluated by both numerical and simulated analysis. The simulation results demonstrate that the gateway selection method is effective and efficient to optimize the throughput for WMNs.     

A delay‐based transport layer mechanism for fair TCP throughput over 802.11 multihop wireless mesh networks

Cities worldwide have planned and implemented large‐scale wireless mesh network (WMN) deployments. These mesh deployments are expected to provide broadband mobile access to the Internet at a low cost to the user. This paper considers the fairness problem affecting nodes in multihop WMNs. Many existing approaches to coping with the fairness problem are unsuitable because they necessitate modifications to the IEEE 802.11 MAC protocol or node queueing operations. Such modifications require a change in hardware/firmware at every node in the WMN. Thus, these approaches are less favorable from the points of view of interoperability and cost. Without modifying the lower layer protocols, this study identifies TCP parameters that impact throughput fairness and proposes an adjustment to these parameters to reduce frame collisions and to improve throughput fairness. Using simple mathematical formulations and ns2 simulations, this study shows that the frame transmissions from each node can be effectively controlled by properly controlling the delayed ACK timer and by using a suitable advertised window. The proposed method, in addition to fairness, requires fewer buffer resources than other methods. Moreover, it is not sensitive to the carrier sense range. It is also simple and easy to deploy. Copyright © 2011 John Wiley & Sons, Ltd.     

GI/Geom/1 queue based on communication model for mesh networks

In mesh networks architecture, it should be permitted to visit the mobile client points. Whereas in mesh networks environment, the main throughput flows usually communicate with the conventional wired network. The so‐called gateway nodes can link directly to traditional Ethernet, depending on these mesh nodes, and can obtain access to data sources that are related to the Ethernet. In wireless mesh networks (WMNs), the quantities of gateways are limited. The packet‐processing ability of settled wireless nodes is limited. Consequently, throughput loads of mesh nodes highly affect the network performance. In this paper, we propose a queuing system that relied on traffic model for WMNs. On the basis of the intelligent adaptivenes, the model considers the influences of interference. Using this intelligent model, service stations with boundless capacity are defined as between gateway and common nodes based on the largest hop count from the gateways, whereas the other nodes are modeled as service stations with certain capacity. Afterwards, we analyze the network throughput, mean packet loss ratio, and packet delay on each hop node with the adaptive model proposed. Simulations show that the intelligent and adaptive model presented is precise in modeling the features of traffic loads in WMNs. Copyright © 2013 John Wiley & Sons, Ltd.