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。     

无线局域网原理与组建

随着无线通信技术的广泛应用，传统局域网络已经越来越不能满足人们的需求，于是无线局域网（Wireless Local Area Network，WLAN）应运而生，且发展迅速。它优越的灵活性和便捷性在网络应用中发挥日益重要的作用。本文详解了无线局域网的特点及组建。     

无线局域网技术在企业中的应用

对于企业来说，信息化起着至关重要的作用，由于传统电缆线的造价高，线路复杂等缺点，逐渐被新兴的无线局域网所替代。本章对无线局域网在企业中的应用进行深入的研究，对应用的问题进行探讨。     

浅谈无线局域网技术在高校中的应用

无线局域网是在有线网络的基础上发展起来的新技术,是无线传输技术在局域网上的应用。作为有线网络的延伸和补充,它对推动高校信息化资源建设的发展起到了重要的作用。同时,也对学校教师,学生的学习,生活方式产生了积极重大的意义。就无线局域网的概念和技术以及在高校中的应用作一个分析和研究。     

无线局域网技术在院前急诊急救中的应用

在这个"网络就是计算机"的时代,伴随着有线网络的广泛应用,以快捷高效,组网灵活为优势的无线网络技术也在飞速发展。无线局域网是计算机网络与无线通信技术相结合的产物。从专业角度讲,无线局域网利用了无线多址信道的一种有效方法来支持计算机之间的通信,并为通信的移动化、个性化和多媒体应用提供了可能。     

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。     

无线局域网在医院中的构建及应用

随着无线网络在技术上日益的成熟,其组网灵活性、良好的可扩展性,逐渐运用到各种复杂的组网环境中,尤其在医疗行业的信息化中得到较好的发展。作为医院有线局域网的补充,无线局域网络有效地克服有线网络的弊端,在病区查房、床边护理、呼叫通信、护理监控、药品配送与管理等方面逐步得到应用,成功部署无线网络,对提高医护人员工作效率和救治质量发挥越来越重要的作用。     

无线局域网设计

无线局域网是计算机网络与无线通信技术相结合的产物。伴随着有线网络的广泛应用,以快捷高效,组网灵活为优势的无线网络技术也在飞速发展。本文对无线局域网的设计进行了阐述。从理论和工程设计实践多角度对无线局域网的构架、设计、建设各方面进行了论述,希望能够对WLAN的设计和建设有所裨益。     

无线局域网中的安全防范策略

随着应用范围的增大,无线局域网的安全性引起人们的关注。通过对无线局域网技术的工作过程进行分析,探讨无线局域网络的安全技术,进一步深入分析并综合论述各种不同角度的安全防范策略。     

对无线局域网网络监测系统的探讨

在当前的时代中,人们对工作生活中的无线局域网的用途越来越广泛,它不仅能够在特定的范围之内,实现局域内的文件传输以及信息的传递工作,同时也提高了办公效率。所以在对无线局域网网络有个好的监测系统就显得尤为重要了。本文作者将对系统框架进行详细说明,同时也将为其提供相应的WLAN协议相应的设计方案,并对网络监测系统结构、硬件组成等相关结构进行明确的说明。     

IP核心网中VoIP业务服务质量的初步研究

通过对比传统电话网的语音业务特点对IP核心网中的VoIP业务流进行了模拟,并通过仿真对IP核心网中VoIP业务流特性进行了观察分析。结果发现,大量VoIP业务汇聚产生的业务流具有突发性小、较平稳的流量特性,因而不必为其分配过多的带宽资源;研究了Internet自相似业务流特性对VoIP业务性能的影响,提出了在VoIP业务中采用高优先调度机制等技术来保障VoIP服务质量的网络设计原则。     

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.     

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.     

基于语音流统计特性的VoIP容量分析与提升算法

在研究IEEE 802.16标准关于VoIP传输机制的基础上,指出语音流的静默特性严重制约了VoIP的容量.通过分析VoIP业务流的统计特性得出了在统计复用情况下VoIP的容量极限.提出了一种基于统计复用的带宽调度方法及其实现算法,以克服由于语音静默带来的语音速率波动.仿真结果表明,该调度方法与UGS(unsolicited grant service)调度相比能够显著提升VoIP的容量,同时使BS和SS之间的VoIP丢包率和传输时延保持在0.02%和5.1ms以下.     

Semi-Markov modeling of dependability of VoIP network in the presence of resource degradation and security attacks

Nowadays VoIP has become an evolutionary technology in telecommunications. Hence it is very important to study and enhance its dependability attributes. In this paper, an analytical dependability model for VoIP is proposed. The study is focused on analyzing the combined effects of resource degradation and security breaches on the Quality of Service (QoS) of VoIP, to enhance its overall dependability. As a preventive maintenance policy to prevent or postpone software failures which cause resource degradation, software rejuvenation is adopted. The dependability model is analyzed using semi-Markov process which captures the effects of non-Markovian nature of the time spent at various states of the system. The steady-state as well as the time-dependent analysis of the dependability model is presented. The steady-state results are obtained analytically, whereas the time-dependent results are obtained from simulation. Also, the analytical model is validated via simulation. The model analysis using a numerical example indicates the feasibility of our approach. Various dependability attributes such as availability, reliability and confidentiality are also obtained. A comparative study is also done between our proposed model and the existing models.     

VoIP技术及其应用

文章叙述了语音在互联网络上传输VoIP(Voice over IP network)的关键技术、国际标准以及VoIP的应用和发展状况。文章对VoIP的技术体系结构进行了详细阐述，重点介绍了语音在IP网络上传输时的技术难题和保证VoIP语音通讯质量QoS(Quality of Service)的关键技术。     

一种支持多跳无线网QoS业务的MAC层接入协议

提供一定的服务质量保证(QoS)是多跳无线网络研究中的热点和难点,本文基于TDMA/FDMA机制提出了一种支持多信道多跳无线网络话音级QoS业务的MAC层接入协议RA/SRN。该协议以RBRP协议思想为基础,针对无线信道中隐藏、暴露终端造成的信道利用率降低和分组冲突问题进行改进设计,减小了信道冲突概率,提高了信道利用率,降低了信道接入时延,为网络层QoS路由协议提供了良好的支持。     

Exposure of the general public due to wireless LAN applications in public places

The typical exposure caused by wireless LAN applications in public areas has been investigated in a variety of scenarios. Small-sized (internet café) and large-scale (airport) indoor scenarios as well as outdoor scenarios in the environment of access points (AP) supplying for residential areas and public places were considered. The exposure assessment was carried out by numerical GTD/UTD computations based on optical wave propagation, as well as by verifying frequency selective measurements in the considered scenarios under real life conditions. In the small-sized indoor scenario the maximum temporal peak values of power density, spatially averaged over body dimensions, were found to be lower than 20 mW/m(2), corresponding to 0.2% of the reference level according to the European Council Recommendation 1999/519/EC. Local peak values of power density might be 1-2 orders of magnitude higher, spatial and time-averaged values for usual data traffic conditions might be 2-3 orders of magnitude lower, depending on the actual data traffic. In the considered outdoor scenarios, exposure was several orders of magnitude lower than in indoor scenarios due to the usually larger distances to the AP antennas.