无线网络在高校图书馆的应用

文章论述了在高校图书馆搭建无线网络的优越性和必要性,探讨图书馆架构无线网络的可行性方案,提出组建无线网络的方法及应注意的问题。

信息网络化 无线走天下——思科无线网络解决方案在美国医院的应用

在医疗系统先进的美国,政府按照“健康保险便携与责任法案”(HIPAA)颁布的新保密标准即将施行,这些大都是患者信息的保密标准,涉及到数据传输的安全性。面对加强无线安全这个医院IT系统需要考虑的重要因素,CiscoAironet可以为医院提供能够满足HIPAA标准的保护等级。 思科Aironet系列提供了全面的无线网络解决方案。包括Cisco Aironet340/350系列无线网桥、无线网络接入点和无线网卡。Cisco Aironet 340/350系列产品兼容IEEE 802.11 b,其互操作性已通过无线以太网兼容性联盟(WECA)的Wi—Fi认证,它采用直序扩频技术,可以工作在2.4GHz频段,最高速率11 Mbps,与固定网络的速率相差无几。

5G网络技术特点及无线网络规划方案

在我国通信事业发展中,通信技术在不断进行跃迁式更新,在4G技术得到普遍应用之后,业界学者已经在积极探讨5G网络技术的构建与应用,本文就5G网络技术特点进行了分析,而后探讨了无线网络规划的情况。

无线网络信号不稳定的原因及解决方法

针对无线网络传输速率低、信号质量不稳定等缺点,从无线网络连接设备、设备间配合等方面进行分析,明确问题所在,提出解决方案。无线网络设备方面存在的主要问题包括硬件产品质量、软件驱动程序优化程度及设备智能化、兼容性程度等三个方面。设备间配合问题主要包括设备网络配置是否匹配,设备间距离、位置是否符合要求,不同无线网络设备信道干扰问题如何避免等三个方面。

无线Mesh网络在校园生活中的应用

无线Mesh网络(Wireless Mesh Network)即无线网状网,是一种新型的宽带无线网络结构,是高速率高容量的分布式网络。本文论述了校园无线Mesh网络在国内外研究的现状,无线Mesh网络在校园生活中的应用及关键技术。同时对渤海大学校园网进行分析,并提出了一种基于无线Mesh网络的渤海大学校园网络的解决方案。

无线校园网络的建设实践

互联网不断延伸,移动办公的需求日益增加,华东理工大学在关注传统校园网络建设的同时,也一直在努力提高校园网络使用的方便和快捷性,将网络不断延伸拓展到每一个角落。本文拟介绍了有关无线网络的技术标准以及华东理工大学无线网络建设的阶段、现状和未来的发展规划。

无线强警

随着信息化建设的不断发展，政府各部门都将如何构建一个安全、高效的网络系统作为政府信息化发展目标之一。在国家提出“以公安信息化工作为核心，以‘科技强警’为目标”的国家公安信息化工程(即“金盾工程”)的建设要求后，经过几年的建设，公安系统从公安部到各省市县的一、二、三级网络已经基本建成。

Multiple k-hop clusters based routing scheme to preserve source-location privacy in WSNs

Privacy is becoming one of the most notable challenges threatening wireless sensor networks(WSNs).Adversaries may use RF(radio frequency) localization techniques to perform hop-by-hop trace back to the source sensor's location.A multiple k-hop clusters based routing strategy(MHCR) is proposed to preserve source-location privacy as well as enhance energy efficiency for WSNs.Owing to the inherent characteristics of intra-cluster data aggregation,each sensor of the interference clusters is able to act as a fake source to confuse the adversary.Moreover,dummy traffic could be filtered efficiently by the cluster heads during the data aggregation,ensuring no energy consumption be burdened in the hotspot of the network.Through careful analysis and calculation on the distribution and the number of interference clusters,energy efficiency is significantly enhanced without reducing the network lifetime.Finally,the security and delay performance of MHCR scheme are theoretically analyzed.Extensive analysis and simulation results demonstrate that MHCR scheme can improve both the location privacy security and energy efficiency markedly,especially in large-scale WSNs.

A Cooperative MIMO Transmission Scheme for Cluster-based Wireless Sensor Networks

Wireless sensor network is becoming more and more popular in recent years, but energy- constrained characteristic of sensor nodes is one of the critical issues that we must consider in system design. In this paper, a cluster-based virtual VBLAST transmission scheme is proposed to achieve energy savings for energy-constrained wireless sensor networks. In the proposed scheme, instead of using cluster member as cooperative nodes, multiple cluster heads cooperate to form virtual antenna array so that V-BLAST based virtual MIMO transmission can be implemented. Based on the communication energy consumption model, a way to optimize the parameters for the scheme is given. In addition, detailed simulation is performed to evaluate the performance of the proposed scheme for both densely and sparsely deployed sensor networks. Theoretical analysis and simulation results verify the energy efficiency of the proposed scheme.

Energy-Efficient Transmission Scheme for Mobile Data Gathering in Wireless Sensor Networks

Energy conservation in Wireless Sensor Networks (WSNs) has always been a crucial issue and has received increased attention in the recent years. A transmission scheme for energy-constrained WSNs is proposed in this paper. The scheme, called MIHOP (MIMO and Multi-hop), combines cluster-based virtual MIMO and multi-hop technologies. The multihop mode is employed in transmitting data when the related sensors are located within a specific number of hops from the sink, and the virtual MIMO mode is used in transmitting data from the remaining sensor nodes. We compare the energy consumption of different transmission schemes and propose an algorithm for determining the optimal hop count in MIHOP. A controllable mobile sink that reduces the energy consumed in sensor transmission is also adopted for data collection. The theoretical analysis and the Monte Carlo simulation demonstrate that the proposed scheme significantly outperforms individual virtual MIMO, multi-hop technologies, and double-string networks in terms of energy conservation. The energy consumption levels under the MIHOP scheme are approximately 12.98%, 47.55% and 48.30% less than that under virtual MIMO schemes, multi-hop networks and doublestring networks, respectively.

WAP技术在远程教育中的应用实践

WAP技术将Internet与移动电话技术结合起来,使随时随地访问丰富的互联网络资源成为现实。现代远程教育是指教、学双方准永久性分离、利用计算机及其网络技术把音、视频以及文本等课程信息传输到非课堂区域的一种教育形式。本文根据WAP技术及远程教育特点,提出了一套在远程教育中应用WAP技术的方案。

Scheduling Scheme for Cellular-Based Machine-Type Communication

Cellular-based Machine-Type Communication (MTC) will become more and more important in the near future for the advantage of the long-distance wireless communication.However,a large number of MTC applications introduce heavy load to cellular network.MTC traffic scheduling schemes are proposed to avoid congestion in this paper.Our approaches are based on the delay-tolerance of MTC traffic.Some MTC traffic is postponed until the network load becomes light.Moreover,our scheme efficiently utilizes the bandwidth resources reserved for handover in traditional cellular network.Simulation results show that the utility usage of radio resources is improved and the congestion probability is reduced.

A timeslot assignment scheme for cluster-tree based wireless sensor network

Many efforts have been made to develop time division multiple access （TDMA） slots allocation in a multi-hop converge-cast wireless sensor network （WSN）, however, most of them either use complex algorithm or concern frames only without simultaneous transmission in a single slot. In this paper, we present a timeslot assignment scheme for cluster-tree-based TDMA WSN, co：＇ering three frequently used working modes in practical applications. The shortest frame formed can guarantee real-time conununication and is also facilitated for message and slot integration, since timeslots allocated to a single node are continuous. During allocation processes, the algorithms are distributed and light-weighted. The experiment resulted from a WSN prototype system shows that our scheme can achieve a good reliability.

On Channel Assignment for Multicast in Multi-Radio Multi-Channel Wireless Mesh Networks:A Survey

The major challenge faced by wireless mesh networks is the capacity reduction caused by interference,and interference can be reduced or even eliminated through appropriate channel assignment.This article presents a comprehensive survey of channel assignment schemes for multicast in multi-radio multi-channel wireless mesh networks.We analyze the state-of-the-art channel assignment schemes for multicast and provide comprehensive taxonomy of the latest work.In general,we classify the channel assignment schemes for multicast into two types,that is,sequential multicast routing and channel assignment(SMRCA)and joint multicast routing and channel assignment(JMRCA).Detailed review of channel assignment schemes in each category is provided.Possible future research directions and corresponding solutions are also explored to motivate research interests in the field of channel assignment for multicast in wireless mesh networks.

Partially Overlapped Channels- and Flow-Based End-to-End Channel Assignment for Multi-Radio Multi-Channel Wireless Mesh Networks

Capacity reduction is a major problem faced by wireless mesh networks. An efficient way to alleviate this problem is proper channel assignment. Current end-toend channel assignment schemes usually focus on the case where channels in distinct frequency bands are assigned to mesh access and backbone, but actually backbone network and access network can use the same IEEE 802.11 technology. Besides, these channel assignment schemes only utilize orthogonal channels to perform channel assignment, and the resulting network interference dramatically degrades network performance. Moreover, Internet-oriented traffic is considered only, and peerto-peer traffic is omitted, or vice versa. The traffic type does not match the practical network. In this paper, we explore how to exploit partially overlapped channels to perform endto-end channel assignment in order to achieve effective end-to-end flow transmissions. The proposed flow-based end-to-end channel assignment schemes can conquer the limitations aforementioned. Simulations reveal that loadaware channel assignment can be applied to networks with stable traffic load, and it can achieve near-optimal performance; Traffic-irrelevant channel assignment is suitable for networks with frequent change of traffic load,and it can achieve good balance between performance and overhead. Also, partially overlapped channels' capability of improving network performance is situation-dependent, they should be used carefully.

Rate Allocation Scheme for Machine-to-Machine Service Based on 3GPP in Heterogeneous Wireless Networks

In this study,an explicit adaptive traffic allocation scheme for Machine-to-Machine(M2M)service is proposed to achieve optimum distribution in heterogeneous networks.Based on the characteristics of M2M services,the presented scheme is formulated as a convex optimization problem that maximises the utility of the M2M service,and then determines how to allocate the total rate among the multiple access networks.The analysis and numerical simulations indicate that the proposed scheme makes a significant improvement in performance compared with the traditional schemes.

A Resource Scheduling Scheme for Spectrum Aggregation in Cognitive Radio Based Heterogeneous Networks

In spectrum aggregation(SA), two or more component carriers(CCs) of different bandwidths in different bands can be aggregated to support wider transmission bandwidth. The current resource scheduling schemes for spectrum aggregation are not optimal or suitable for CR based heterogeneous networks(Het Nets). Consequently, the authors propose a novel resource scheduling scheme for spectrum aggregation in CR based Het Nets, termed as cognitive radio based resource scheduling(CR-RS) scheme. CR-RS has a three-level structure. Under a dynamic traffic model, an equivalent throughput of the CCs based on the knowledge of primary users(PUs) is given. On this basis, the CR users data transmission time of each CC is equal in CR-RS. The simulation results show that CR-RS has the better performance than the current resource scheduling schemes in the CR based Het Nets. Meanwhile, CR-RS is also effective in other spectrum aggregation systems which are not CR based HetNets.

Link Maintenance Scheme for OFDM-Based Cognitive Radio Ad Hoc Networks

Transmission among the cognitive users(CUs)' is always interrupted by the primary users(PUs)' reclaim of the spectrum and the fading effect of wireless channels.To maintain reliable continuous communication among CUs,an efficient scheme for link maintenance in OFDM-based cognitive radio Ad Hoc networks is proposed in this paper.In the scheme,redundant sub-channels(RSC) are employed by CUs to tackle the outage problem caused by the PUs' reclaim of the spectrum and wireless fading effect in the transmission.Meanwhile,backup sub-channels(BSC) are arranged to help select sub-channels with better channel quality.Additionally,to lower the overhead and improve the accuracy of the spectrum sensing,a partial sensing module is designed to enable the CUs to inherit and update the original idle spectrum list until it expires.Simulation results show that the proposed scheme can realize higher throughput and lower sensing overhead with slight reduction of the forced termination probability(FTP) performance compared to the existing approaches.

Dynamic Cell Range Expansion-based Interference Coordination Scheme in Next Generation Wireless Networks

Deploying Picocell Base Station(PBS) throughout a Macrocell is a promising solution for capacity improvement in the next generation wireless networks.However,the strong received power from Macrocell Base Station(MBS) makes the areas of Picocell narrow and limits the gain of cell splitting.In this paper,we firstly propose a Dynamic Cell Range Expansion(DCRE) strategy.By expanding the coverage of the cell,we aim to balance the network load between MBS and PBS.Then,we present a cooperative Resource block and Power Allocation Scheme(coRPAS)based on DCRE.The objective of coRPAS is to decrease interference caused by MBS and Macrocell User Equipments,by which we can expand regions of Picocell User Equipments.Simulation results demonstrate the superiority of our method through comparing with other existing methods.