"Real-time performance evaluation of wireless local area networks (WLANs) is an extremely challenging topic. The major drawback of real-time performance analysis in actual network installations is a lack of repeatability due to uncontrollable interference and propagation complexities. These are caused by unpredictable variations in the interference scenarios and statistical behavior of the wireless propagation channel. This underscores the need for a Radio Frequency (RF) test platform that provides isolation from interfering sources while simulating a real-time wireless channel, thereby creating a realistic and controllable radio propagation test environment. Such an RF-isolated testbed is necessary to enable an empirical yet repeatable evaluation of the effects of the wireless channel on WLAN performance. In this thesis, a testbed is developed that enables real-time laboratory performance evaluation of WLANs. This testbed utilizes an RF-isolated test system, Azimuthâ„¢ Systems 801W, for isolation from external interfering sources such as cordless phones and microwave ovens and a real-time multipath channel simulator, Elektrobit PROPSimâ„¢ C8, for wireless channel emulation. A software protocol analyzer, WildPackets Airopeek NX, is used to capture data packets in the testbed from which statistical data characterizing performance such as data rate and Received Signal Strength (RSS) are collected. The relationship between the wireless channel and WLAN performance, under controlled propagation and interference conditions, is analyzed using this RF-isolated multipath testbed. Average throughput and instantaneous throughput variation of IEEE 802.11b and 802.11g WLANs operating in four different channels - a constant channel and IEEE 802.11 Task Group n (TGn) Channel Models A, B, and C - are examined. Practical models describing the average throughput as a function of the average received power and throughput variation as a function of the average throughput under different propagation conditions are presented. Comprehensive throughput models that incorporate throughput variation are proposed for the four channels using Weibull and Gaussian probability distributions. These models provide a means for realistic simulation of throughput for a specific channel at an average received power. Also proposed is a metric to describe the normalized throughput capacity of WLANs for comparative performance evaluation."

Made available in DSpace on 2016-04-04T18:31:27Z (GMT). No. of bitstreams: 1 Manoel Peluso de Carvalho Filho.pdf: 1548469 bytes, checksum: 813f063c4ea17788aa795465c9e6e6f5 (MD5) Previous issue date: 2008-11-24 / Nowadays, the use of the wireless network technology has grown mainly motivated by the price of equipments, ease of installation, network maintenance and expansion of technical safety. The more you use the wireless network resource, the better should be the treatment related to its safety aspect. As the security level increases, the amount of information transmitted between the equipment decreases. This thesis aims to analyze the performance of WLAN network with the implementation of WEP and WPA / TKIP security protocols in an environment that uses applications whose characteristic is to generate small packets on the network. The LanTraffic TM software is used to generate traffic and also to capture the transmission rate in Kbps that flows through the stations. Three scenarios are simulated varying in the distance between the equipments. For each scenario, a comparative study was made and the WLAN behavior without the security resource analyzed, then it was analyzed with the WEP fitted and finally with the WPA/TKIP configured. To develop the experiments it was used a WLAN network in a controlled environment in the Laboratory Research on Radio System in PUC Campinas. Therefore, there is not external interference in the signal transmitted by equipments. / A utiliza??o da tecnologia de rede sem fio tem crescido ultimamente motivado principalmente pelo pre?o dos equipamentos, facilidade de instala??o, manuten??o da rede e amplia??o das t?cnicas de seguran?a. Quanto mais se utiliza o recurso de rede sem fio maior tem de ser o tratamento em rela??o ao aspecto de seguran?a. A medida que aumenta o n?vel de seguran?a, decresce a quantidade de informa??o transmitida entre os equipamentos. Esse trabalho visa analisar o desempenho de rede WLAN(Wireless Local ?rea Network) com a implementa??o dos protocolos de seguran?a WEP(Wired Equivalent Privacy) e WPA/TKIP(WI-FI Protected Access / Temporal Key Integrity Protocol). ? utilizado o software LanTrafficTM para gerar tr?fego na rede e tamb?m para capturar a taxa de transmiss?o em Kbps trafegados entre as STAs. S?o emulados tr?s cen?rios variando a dist?ncia entre os equipamentos. Para cada cen?rio foi confeccionado um comparativo e analisado o comportamento da WLAN configurado sem seguran?a, com o WEP habilitado e finalmente com o WPA/TKIP configurado. Para executar os experimentos utilizou-se uma rede WLAN no laborat?rio de pesquisa em sistema de r?dio (LP-SiRa) da PUC Campinas em um ambiente controlado. Com isso n?o h? interfer?ncias na transmiss?o dos sinais emitidos pelos equipamentos Ou seja, sem interfer?ncia externa no sinal transmitido entre os equipamentos.