MOMO-OFDM技术及其在局域网中应用

采用正交频分复用(OFDM)可以提高频带利用率.采用MIMO技术可以提高信道容量和信道可靠性,降低误码.MIMO-OFDM将OFDM技术与MIMO技术结合起来,在不增加带宽与功率的前提下,可以增加数据的传输数率,被视为下一代无限局域网的核心技术.文章简单介绍了MIMO-OFDM技术的原理.并探讨了其在下一代高速无限局域网中的应用.     

WLAN标准的演进及其在无线校园网中的应用研究

通过阐述无线局域网(WLAN)相关技术的特点、应用现状及技术演进过程,对其中的第五代WLAN标准——802.11ac协议进行了重点分析,从与802.11ad协议对比、基本原理结构及其应用场合等方面进行了介绍。根据当前的技术进展,总结了802.11ac协议采用的协议框架、核心关键技术、使用频段、PHY层数据速率、客户端支撑能力以及将来的应用场景等五个方面的内容。结合西安科技大学校园网建设的现状和用户群体规模特点,提出了采用802.11ac协议和Aerohive公司相关的无线网络设备搭建校园网的无线网络部分,同时利用前期建设成果校园网网络计费认证管理系统,实现校园网有线和无线网络的统一认证、计费等管理。通过该无线网络的建设,进一步方便了师生对信息技术的需求,更好的支撑了本科教学工作。     

On service differentiation in mobile Ad Hoc networks

A network model is proposed to support service differentiation for mobile Ad Hoc networks by combining a fully distributed admission control approach and the DIFS based differentiation mechanism of IEEE802.11. It can provide different kinds of QoS (Quality of Service) for various applications. Admission controllers determine a committed bandwidth based on the reserved bandwidth of flows and the source utilization of networks. Packets are marked when entering into networks by markers according to the committed rate. By the mark in the packet header, intermediate nodes handle the Received packets in different manners to provide applications with the QoS corresponding to the pre-negotiated profile.Extensive simulation experiments showed that the proposed mechanism can provide QoS guarantee to assured service traffic and increase the channel utilization of networks.     

Performance analysis of IEEE 802.11 DCF networks

This paper presents an analytical saturation throughput model of IEEE 802.11DCF （distributed coordination function） with basic access in ad hoc mode. The model takes into account freezing of the backofftimer when a station senses busy channel. It is shown that taking into account this feature of DCF is important in modeling saturation throughput by yielding more accurate and realistic results than models known from literature. The proposed analytical model also takes into account the effect of transmission errors. All essential features of the proposed analytical approach are illustrated with numerical results. The presen- tation of the model is proceeded by an overview of approaches to IEEE 802.11 network performance evaluation presented in the literature.     

Theft in a wireless world

I explore philosophically the phenomenon of home wireless networks as used to share broadband Internet connections. Because such networks are frequently unsecured, third parties can use them to access the Internet. Here I consider carefully whether this kind of behaviour should be properly called theft. I begin with a brief non-technical introduction to 802.11 wireless networks. Subsequently, I present a four part argument – appealing to the unsecured nature of the networks discussed, entrenched software and hardware behaviours, trespass law, and the openness of ‹public park’ spectrum – suggesting that this kind of behaviour is permissible and should not be construed as theft. Substantively, I conclude that, despite the quite compelling considerations that these arguments bring to bear, this behaviour is theft. Additionally, I draw attention to significant flaws in the design and implementation of wireless technology (specifically in the out-of-the-box configuration for wireless access points and in the wireless connectivity of early versions of Windows XP) that facilitate the intentional and unintentional theft of Internet bandwidth. I suggest some simple mechanisms that could be incorporated into the technology which would serve to remove the ethical ambiguity in its usage by third parties, including adding the ability for a network owner to explicitly mark her network as not for public use,␣and changes to default hardware and software behaviours. I conclude by encouraging increased use of value-sensitive design practices in the development of future wireless technologies.     

无线局域网与IEEE802.11

无线局域网将对网络技术的发展造成深刻的影响。本文简要介绍了无线局域网各方面的情况, 包括其背景、主要技术、组网实现以及IEEE802. 11 物理层与MAC 层协议规范, 并分析了它的局限与发展。     

无线局域网在现代图书馆网络构建中的应用

阐述了无线局域网的技术基础及构建无线局域网时应注意的问题,提出高校图书馆构建无线局域网是为了弥补有线网络的不足,同时指出无线局域网将极大地方便读者利用便携式工具随时随地获取信息。     

基于Linux的802.11b无线网络MAC层切换的分析和实现

切换过程对无线移动网络质量有重大的影响,而现阶段的802.11b/g对切换的支持并不理想.文章从理论上分析了802.11b无线网络MAC层切换原理和过程,根据造成切换延迟和丢包的因素,提出了切换算法的改进策略,并且基于Linux系统和开源代码对该算法完成了软件实现.实验结果表明,改进算法可有效提高无线网络MAC层切换的速度.     

高速无线局域网信道差错控制研究

为了解决无线局域网传输差错多、信道时变性强的问题,本文提出了高速无线局域网信道FEC纠错的基本方法,并对其信道的自适应差错控制机制进行了深入的研究,着重对IEEE802.11b现有的重传纠错机制进行改进,加入了FEC纠错,并对传输信道的可靠性与吞吐量进行了研究与仿真.     

智能无线校园网络部署和探究

随着无线网络的迅速发展和日益增加的移动办公需求,无线网络逐渐成为不少高校信息化网络的重要组成部分,本文介绍了无线网络的技术标准以及智能无线校园网络的部署探究,从而使用户智能安全的接入和使用无线校园网络．