无线互联的发展趋势——无线局域网的最新标准、技术及应用

无线局域网可当作有线局域网的扩展来使用，也可独立作为有线局域网的替代设施。因此，未来的无线周域网，需要具备更高的传输速度，提供更加便捷的组网技术，能够应用于更加复杂的环境信道下，且系统性能高效稳定。     

嵌入式无线局网安全检测方案的研究与实现

研究了无线局域网数据包捕获技术、无线帧解码技术及无线局域网安全检测方法等技术。采用了无线网卡监听技术，对WLAN中传输的数据帧进行实时监控。通过对数据帧的分析，提出了网络性能测试和802.1x认证的检测方法，并用直观的方式显示无线网络的运行状况。在此基础上，提出了一个完整的无线局域网（WLAN）安全检测方案，并详细介绍了嵌入式WLAN安全检测系统的实现。     

基于无线数据包的分析与仿真

与传统有线网络相比,无线网络更方便,覆盖的范围更广。无线局域网(Wireless LAN,WLAN)是不使用任何导线或传输电缆连接的局域网,无线局域网最通用的标准是IEEE定义的802.11系列标准。本文通过真实无线环境与协议分析软件相结合捕获无线数据包,分析多种数据帧。     

基于无线数据包的分析与仿真

与传统有线网络相比,无线网络更方便,覆盖的范围更广。无线局域网(Wireless LAN,WLAN)是不使用任何导线或传输电缆连接的局域网,无线局域网最通用的标准是IEEE定义的802.11系列标准。本文通过真实无线环境与协议分析软件相结合捕获无线数据包,分析多种数据帧。     

无线局域网技术与标准研究

无线局域网是实现移动计算机网络的关键技术之一，它能够快速、方便地解决以有线局域网方式不易实现的网络信道的联通问题，并可作为有线网络的扩充，具有广阔的应用前景。文章就无线局域网的关键技术及标准进行了介绍，并详细分析比较了每种标准所涉及的技术内涵，最后预期了该技术的发展。     

无线局域网技术系列讲座之二 无线互联的发展趋势——无线局域网的最新标准、技术及应用

无线局域网可当作有线局域网的扩展来使用,也可独立作为有线局域网的替代设施。因此,未来的无线局域网,需要具备更高的传输速度,提供更加便捷的组网技术,能够应用于更加复杂的环境信道下,且系统性能高效稳定。     

有线技术和无线技术混合局域网组建研究

分析了有线局域网和无线局域网的主要特点,提出有线技术和无线技术混合组建局域网的应用需求。以企业内部局域网为例,研究了有线和无线混合组建局域网的基本方案。     

无线局域网MAC机制对TCP性能的影响分析

通过分析和比较IEEE802.11无线局域网分别采用3种典型MAC机制时的TCP性能,深入研究了MAC机制对无线局域网中TCP性能的影响.仿真结果表明,由MAC机制所决定的信道冲突率、MAC帧丢失率、MAC帧传输时延抖动幅度和频率、网络吞吐量和公平性将直接影响无线局域网中TCP的吞吐量、公平性和稳定性.     

WLAN的市场发展

无线局域网是利用无线通信技术在一定的局部范围内建立的网络．是计算机网络与无线通信技术相结合的产物，它以无线多址信道作为传输媒介，提供了传统的有线局域网的功能，使用户能够真正实现随时、随地、随意的宽带网络接入。     

如何选择合适的WALN构架

无线局域网（WLANS）经常作为有线局域网覆盖的有效延伸，目前，我们有两种经常使用的无线局域网构架，它们分别是分布式无线局域网和集中式无线局域网，它们的存在对有线网络的架构上有着各种各样不同的影响。WLAN的基础结构和分布式架构系统各自有它们值得考虑的优点和价值，我们需要根据实际的需要来选择合适的WLAN构架。     

基于OPNET的IEEE802．11信道接入技术仿真研究

信道接入控制技术是实现无线网络节点共享无线信道空间的关键技术。IEEE802．11作为无线局域网的一个重要协议标准,定义了两种信道接入控制方式,分别是分布式协调方式和中心协调方式。本文主要研究了以IEEE802．11协议标准为对象的无线局域网两种信道接入技术的学习和讨论,并运用先进的网络仿真工具OPNET对信道接入技术进行了仿真研究,总结了不同信道接入技术下的无线局域网的网络性能。指出设计网络时需要根据不同情况来选用不同的方式来进行通信。     

无线网络中实时业务的信道预留

随着无线数据服务的流行和多媒体应用需求的增长,需要无线网络能够为不同种类的业务提供有区别的服务质量(QoS),因此如何在无线网络中提供有区分和有保证的服务质量,成为一个非常重要的问题。论文提出了一种在IEEE802.11无线网络中为实时业务提供服务质量保证的有效方法,即通过修改介质访问控制(MAC)层的分布式协调功能(DCF),为实时数据预留信道。当一个节点竞争到信道后,可以连续向同一个目标节点发送多个实时数据帧,称作传送突发(TB,TransmissionBurst),即在一个TB中第一个数据帧将为实时业务预留信道,直到这个TB结束,这样实时业务将比其他业务占有更多的信道资源。仿真结果表明,该方法能够明显改进实时业务的吞吐率和延迟性能,提高无线网络的信道利用率,而且,对DCF的修改没有增加任何控制开销。     

FITAP技术分析及其在医疗信息化中的新应用

和传统的有线接入方式相比,无线网络让网络的使用更自由;无线局域网（WLAN）无需布线,施工简单快捷,让网络实施更方便,成本更低廉;无线可以让工作更高效,已成为很多行业提高生产效率的重要技术手段。本文以基于FITAP的无线局域网（WLAN）为切入点,深入分析了其相对于传统基于FATAP的WLAN的优势,介绍了其在医疗信息化中几个新的应用和关键技术。     

无线局域网安全保密管控技术研究

随着网络的发展和无线Wi Fi业务的应用不断普及,无线局域网安全保密性能得到了广泛的重视。本文对无线局域网的安全体系进行分析,研究无线局域网安全保密管控方案,通过性能测试证明本文所设计的无线局域网安全保密管控方案的可行性。     

无线局域网网络安全措施的改进研究

无线接入网技术是当前国际上的研究热点,无线局域网作为一种无线接入技术得到了迅速的发展,但是随后一系列的研究表明,早期的无线局域网安全机制存在很大的安全隐患。随着无线局域网的不断普及,无线局域网的安全成为了制约无线局域网应用拓展的重要因素之一。本文从无线局域网的安全威胁、无线局域网网络结构、无线局域网安全业务和无线局域网安全方案改进措施四方面进行阐述。     

Supporting QoS in IEEE 802.11e wireless LANs over fading channel

Transferring real-time traffic such as voice and video over wireless LAN networks (WLAN) requires stringent delay and jitter requirements. Recently IEEE 802.11e standard has been emerged to support QoS in WLAN. One of the methods to provide QoS in this standard is Enhanced Distributed Channel Access (EDCA) which benefits form the concept of traffic categories. However, EDCA is a contention based method; therefore it can not guarantee strict QoS required by real-time services without proper network control mechanisms. In this paper, we analyze the effect of loss and delay caused by fading channel on EDCA performance. Then, we propose a modification to the media access scheme, called CAFD (Collision Avoidance with Fading Detection) to elevate the performance against channel failures. Moreover an adjustment for the maximum number of retransmissions is proposed to maintain the delay and jitter requirements of the real-time traffic. The performances of the proposed methods are evaluated by simulations.     

Dynamic slot assignment protocol for QoS support on TDMA-based mobile networks

An efficient bandwidth allocation scheme in wireless networks should not only guarantee successful data transmission without collisions but also enhance the channel spatial reuse to maximize the system throughput. The design of high-performance wireless Local Area Network (LAN) technologies making use of TDMA/FDD MAC (Time Division Multiple Access/Frequency Division Duplex - Medium Access Control) is a very active area of research and development. Several protocols have been proposed in the literature as TDMA-based bandwidth allocation schemes. However, they do not have a convenient generic parameters or suitable frame repartition for dynamic adjustment. In this work, we undertake the design and performance evaluation of a QoS (Quality of Service)-aware scheme built on top of the underlying signaling and bandwidth allocation mechanisms provided by most wireless LANs standards. The main contribution of this study is the new guarantee-based dynamic adjustment algorithm used in MAC level to provide the required QoS for all traffic types in wireless medium especially Wireless ATM (Asynchronous Transfer Mode). Performance evaluation of this approach consists of improving the bandwidth utilization, supporting different QoS requirements and reducing call reject probability and packet latency.     

Energy-balanced cross layer traffic and coding optimality in battery-powered wireless mesh networks

How to prolong the lifetime of multi-hop-multi-path wireless mesh networks powered by finite battery resource is a critical research challenge. In this paper, we strive for energy-balancing to maximize the network lifetime, while improving multimedia service quality via exploring both hop and path diversities. Different from traditional research, which sacrifices throughput for efficient energy utilization in the networks, we proposed a new approach jointly considering 5 factors in a cross layer fashion: the wireless channel condition, the physical layer channel coding redundancy, the application layer traffic rate, the path level energy-balancing of the network, and the Quality of Service (QoS) of multimedia. In the proposed approach, we develop an optimal scheme to allocate path-level multimedia traffic and link-level channel coding redundancy jointly, which minimizes the routers’ battery energy difference while satisfying a lower bound of quality requirement. The simulation results illustrate that the proposed approach can significantly improve the energy-balancing of the multi-hop-multi-path wireless mesh networks by performing the traffic and channel coding control.     

基于IEEE 802.11标准的无线局域网组网方案

叙述了无线局域网的概念、基本原理及其网络标准的演变 ,并就目前无线局域网的研究热点—基于IEEE 80 2 .1 1标准的无线局域网的组网方案及其技术参数进行了论述     

A fair resource allocation protocol for multimedia wireless networks

Wireless networks are expected to support real-time interactive multimedia traffic and must be able, therefore, to provide their users with quality-of-service (QoS) guarantees. Although the QoS provisioning problem arises in wireline networks as well, mobility of hosts and scarcity of bandwidth makes QoS provisioning a challenging task in wireless networks. It has been noticed that multimedia applications can tolerate and gracefully adapt to transient fluctuations in the QoS that they receive from the network. The additional flexibility afforded by the ability of multimedia applications to tolerate and adapt to transient changes in QoS can be exploited by protocol designers to significantly improve the overall performance of wireless systems. This paper presents a fair resource allocation protocol for multimedia wireless networks that uses a combination of bandwidth reservation and bandwidth borrowing to provide network users with QoS in terms of guaranteed bandwidth, call blocking, and call dropping probabilities. Our view of fairness was inspired by the well-known max-min fairness allocation protocol for wireline networks. Simulation results are presented that compare our protocol to similar schemes.