无线局域网(WLAN)安全威胁和解决方法的研究

随着人们对降低成本和获得移动性需求的日益增长,无线局域网的用户数量也正在迅速增加,无线局域网也早已成为人们日常生活不可分割的部分。无线局域网是无线技术与局域网技术相结合的产物。它为数据通信提供一种灵活的方式,但也正是其灵活性引发一些威胁用户隐私和安全的问题。在阐述无线局域网概况的基础上,总结无线局域网存在的三类安全威胁,并归纳现有的一些解决方法,最后就无线局域网的发展提出几点建议。     

解决无线局域网安全问题的几点措施

相对于传统的有线局域网来说,无线局域网技术具备较强的灵活性和以及良好的移动性,因此,获得广泛的应用和推广,并且得到快速的发展。但是,在现阶段,无线局域网所存在的安全问题也不容忽视,国内外相关文献对于无线局域网相关的安全技术的研究还不够全面,必须引起足够的重视。重点阐述解决无线局域网安全问题的几点措施。     

无线局域网在信号系统中的运用分析

本文简要介绍了无线局域网的技术标准、基本结构以及采用无线局域网方式的车——地通信,重点对无线局域网技术在城轨交通信号系统中的工作原理、应用优势和可能存在的问题等进行了分析。     

校园无线局域网安全威胁及解决对策

随着网络科学技术的高速发展,在国家教育部的推动下,很多的学校都选择将无线局域网技术引入到校园网中来,完善现有的校园网。首先对无线局域网的优势、特点等做简单介绍,分析其原理,并根据校园无线局域网的特点,分析目前校园局域网存在的一些安全威胁,并给出相应的解决对策。希望能通过研究给校园无线局域网安全问题提供参考与借鉴。     

无线局域网面临的安全问题及其检测的方法的探索

无线局域网是在互联网中以无线媒体或介质进行通信的网络,彻底避免有线网络线缆对用户的束缚。典型的技术是IEEE802.11系列标准,传输速率在11～54Mbps,802.11n标准的出台使其传输速率最高可达到300Mbps。近年来,无线局域网的发展非常迅速并且得到广泛的应用。然而,无线局域网面临的安全问题也是不容忽视的。基于此,进行关于无线局域网面临的安全问题及其检测的方法的探索具有非常重要的意义。结合当前无线局域网的具体发展状况对无线局域网面临的安全问题及其检测的方法进行深入的探索。     

无线局域网安全浅析

无线局域网得到越来越广泛的应用,在带来方便的同时也带来新的安全问题。因此,从无线局域网的标准,面临的问题做简要分析,并给出解决无线局域网安全问题的防范措施。     

浅析无线局域网的安全性

无线局域网(Wireless Local Area network,WLAN)以其方便、快捷、廉价等优势渐渐成为计算机网络的一个重要的组成部分。然而伴随着WLAN的应用越来越广泛,无线局域网受到越来越多的威胁。本文首先介绍了无线局域网的涵义及其安全技术,然后例举了其威胁因素并由此提出相应的解决措施。     

ATM原理及其在无线局域网中的应用

ATM技术是实现高速综合业务网络的关键技术。本文简要的介绍了ATM的基本原理，协议模型及ATM在无线局域网中的应用即ATM无线局域网技术。     

怎样维护无线局域网的安全

由于现在局域网建网的地域越来越复杂,很多地方应用了无线技术来建设局域网,但是由于无线网络应用电磁波作为传输媒介,因此安全问题就显得尤为突出。本文通过对危害无线局域网的一些因素的叙述,给出了一些应对的安全措施,以保证无线局域网能够安全,正常的运行。     

无线局域网的概况

无线局域网的覆盖范围为几百米,在这样一个范围内,无线设备可以自由移动,其适合于低移动性的应用环境。而且无线局域网的载频为公用频段,无需另外付费,因而使用无线局域网的成本很低。无线局域网带宽更会发展到上百兆的带宽,能够满足绝大多数用户的带宽要求。基于以上原因,无线局域网在市场赢得热烈的反响,并迅速发展成为一种重要的无线接入互联网的技术。但由于无线局域网应用具有很大的开放性,数据传播范围很难控制,因此无线局域网将面临着更严峻的安个问题。本文在阐述无线局域网安全发展概况的基础上,分析了无线局域网的安全必要性,并从不同方面总结了无线局域网遇到的安全风险,同时重点分析了IEEES02．1Ib标准的安全性、影响因素及其解决方案,最后对无线局域网的安全技术发展趋势进行了展望。     

无线局域网上IP语音传输的容量分析

由于无线媒介的易变性，IP语音在无线局域网上传输受到极大的限制。通过对无线局域网媒体接入层机制的分析，考虑了碰撞概率因素，提出了采用马尔可夫链模型来推导在IEEE 80211b/a/g标准下单个接入点同时支持IP语音用户最大容量的方法，计算出针对不同IP语音编码标准如G711, G729和G723.1下的用户容量上限。并在NS2仿真环境下进行结果验证。     

Survey and Analysis of VoIP Frame Aggregation Methods over A-MSDU IEEE 802.11n Wireless Networks

The IEEE 802.11n standard has provided prominent features that greatly contribute to ubiquitous wireless networks. Over the last ten years, voice over IP (VoIP) has become widespread around the globe owing to its low-cost or even free call rate. The combination of these technologies (VoIP and wireless) has become desirable and inevitable for organizations. However, VoIP faces a bandwidth utilization issue when working with 802.11 wireless networks. The bandwidth utilization is inefficient on the grounds that (i) 80 bytes of 802.11/RTP/UDP/IP header is appended to 10–730 bytes of VoIP payload and (ii) 765 µs waiting intervals follow each 802.11 VoIP frame. Without considering the quality requirements of a VoIP call, be including frame aggregation in the IEEE 802.11n standard has been suggested as a solution for the bandwidth utilization issue. Consequently, several aggregation methods have been proposed to handle the quality requirements of VoIP calls when carried over an IEEE 802.11n wireless network. In this survey, we analyze the existing aggregation methods of VoIP over the A-MSDU IEEE 802.11n wireless standard. The survey provides researchers with a detailed analysis of the bandwidth utilization issue concerning the A-MSDU 802.11n standard, discussion of the main approaches of frame aggregation methods and existing aggregation methods, elaboration of the impact of frame aggregation methods on network performance and VoIP call quality, and suggestion of new areas to be investigated in conjunction with frame aggregation. The survey contributes by offering guidelines to design an appropriate, reliable, and robust aggregation method of VoIP over 802.11n standard.     

嵌入式Linux下无线网卡驱动程序设计

本文采用了搭载ARM11处理器的开发平台,无线网络芯片采用Marvell88W8686芯片,内核采用linux2．6．28内核,介绍了WLAN和无线网卡硬件组成,详细分析了无线网卡在嵌入式Linux下的驱动程序的各个模块功能,在此基础上测试无线网络的性能。     

Dual power-saving modes for voice over IP traffic supporting voice activity detection

In the context of the IEEE 802.16e standard, a dual power-saving mode (DPSM) algorithm for voice over IP (VoIP) traffic whose voice codec supports voice activity detection is proposed. The proposed algorithm utilises the inactivity of the voice codec of each conversing party during mutual silence periods. Using the suggested method, the length of the sleep intervals varies during mutual silence periods, while during talk-spurt periods it is fixed according the VoIP packet generation ratio. The performance of the proposed DPSM algorithm for the average packet-buffering delay in the base station (BS) and the energy consumption of a mobile station (MS) is evaluated numerically and validated with the aid of computer simulation. The results show that when the proposed combined method is used, the energy consumption of an MS is considerably less when a PSM that only uses sleep intervals of a fixed length is operating. This improvement in performance comes at the cost of greater packet-buffering delay in the BS.     

Design and implementation of the push-to-talk service in ad hoc VoIP network

Push-to-talk (PTT) is a walkie-talkie like service which performs an efficient and instant voice over Internet protocol (VoIP) communication in mobile ad hoc network especially for certain circumstances, such as battle field and earthquake or disaster relief. The authors have designed and implemented the PTT mechanism in ad hoc VoIP network. The PTT server and user agent combined with the pseudo session initiation protocol (SIP) server in the implementation provide the PTT service without standalone SIP server support. The authors also conduct the experimental measurements, in terms of delay and packet loss, in the test-bed to demonstrate the realisation of PTT service in ad hoc VoIP network.     

IP家庭网络的服务质量架构研究

经过对IP网络和家庭网络服务体系的客观分析,提出了基于策略的IP家庭网络QoS保证架构.它融合了数据平面、控制平面和管理平面,可以与现有的IPQoS体系无缝连接,支持高质量的语音和视频服务.该结构对其他设备的依赖程度低,适应异构、复杂的家庭网络环境.通过在863项目中的应用,验证了该系统架构对IPTV、VoD及VoIP等多媒体业务的支持.     

Measurement of the effects of temporal clipping on speech quality

This paper investigates the effects of temporal clipping on perceived speech quality. Temporal clipping usually results from voice activity detection (VAD), or line echo canceller's nonlinear processor, and the clipped speech portions are replaced by comfort noise. A nonintrusive algorithm is proposed to predict speech quality based on the clipping statistics. Mean opinion score (MOS) is used as a metric for speech quality and is measured by perceptual evaluation of speech quality (PESQ). The impacts of speech frame size and noise spectrum on the algorithm are also investigated. The results show that the proposed algorithm can efficiently predict the speech quality. The correlation coefficient between the prediction and the measurement is about 0.975, and the root mean square error for the prediction is 0.20 MOS. The algorithm can be used as an integral part of a general speech quality assessment scheme in voice over Internet protocol (VoIP).     

宽带CDMA无线多媒体接入系统的研究

提出了可变传输速率的宽带CDMA扩频调制方法、非平衡功率控制算法以及自适应接入速率的无线接入方法。基于上述技术,给出了由基站和多媒体终端组成的实验系统参数。该系统实现了舆速率分别为8kbp和144skbps的语音和数据通信。     

无线接入点WAPI认证机制的研究与实现

随着无线局域网技术的广泛应用，新的无线局域网安全标准被提出以增强无线局域网的安全性能。在分析WAPI(WLAN Authentication and Privacy Infrastructure)标准的技术特征和基本架构的基础上，介绍了无线接入点对WAPI认证机制的实现机理和具体流程，并对WAPI认证机制的性能进行测试分析。     

VoIP Diffusion among New Entrants: A Path Dependent Process

The path dependency literature provides insights on the dynamic allocation processes in which events are non-ergodic and have multiple absorbing states. Technological change belongs to this class of processes. This paper contributes to this conceptual framework by analysing the distinction between path and past dependence. The aim is to investigate how firms implement new innovations in localized technological changes. This conceptual framework is developed to present a longitudinal case study describing the history of VoIP (Voice over Internet Protocol) diffusion using data triangulation. From the empirical findings, it emerges that new entrants have applied the technology with creativity, following a path dependent process, offering free voice communication, while incumbents have applied the technology within a past dependent pattern and thus the benefits to their customers have been reduced and delayed.