Made available in DSpace on 2016-04-04T18:31:20Z (GMT). No. of bitstreams: 1 Alessandra B Bandeira.pdf: 1200038 bytes, checksum: 316684811248760f05faf3fdda1844f3 (MD5) Previous issue date: 2007-10-30 / This work investigates VoIP (Voice over IP) performance over WLAN (WVoIP) through qualitative and quantitative point of view, considering degradation in indoor environment. The results was obtained through a channel emulator to produce the Weibull distribution. Measurements results with a robot showed that this distribution is adequate to represent WLAN environment instability. The test utilized the CODECs (Coder Decoder) G711 and GSM (Global System for Mobile Communications). The work presents results that indicate the effect of the instability of wireless environment in the VoIP performance. The results indicate a significant variation of voice quality, considering the severity of the phenomena emulated. The behaviors of the CODECs are evaluated considering the different characteristics of bandwidth and robustness. / O trabalho investiga de forma quantitativa e qualitativa o desempenho de VoIP (Voz sobre IP) em uma rede WLAN (Wireless Local ?rea Network), denominado WVoIP, (Wireless VoIP) considerando degrada??o em ambiente indoor. Para atingir esse objetivo foram realizados testes utilizando um emulador de canal capaz de produzir fen?menos de propaga??o com distribui??o de Weibull. Medidas mostram que esta distribui??o ? adequada para avalia??o de instabilidade em redes WLANs. S?o utilizados dois codecs de voz: G711 e GSM (Global System for Mobile Communications). O trabalho apresenta resultados que indicam o efeito dos fen?menos de instabilidade das redes sem fio no desempenho de VoIP, que revelam varia??es significativas na qualidade de voz em fun??o da intensidade dos fen?menos emulados. S?o analisadas as quest?es relativas aos codecs de voz que possuem caracter?sticas de banda e robustez diferentes.

Made available in DSpace on 2016-04-04T18:31:26Z (GMT). No. of bitstreams: 1 Adenilson Boccato de Almeida.pdf: 2733171 bytes, checksum: 5b2d37bdad4b16ff26ccb172bbd6fbfc (MD5) Previous issue date: 2008-12-18 / This dissertation examines the quality of the transmission of VoIP (Voice over IP) in wireless LAN (Local Area Network Wireless). To achieve this objective tests were performed on the bench using voice codecs G729, G711, G723 and GSM analyzing characteristics of delay and loss of packets. The paper presents results that indicate the effect of the phenomena of instability of wireless networks in the performance of VoIP. These variations show significant changes in the quality of voice depending on the used environment and the distance between the transmitter and receiver. / Esta disserta??o analisa a qualidade da transmiss?o do VoIP (Voz sobre IP) em rede WLAN (Wireless Local ?rea Network). Para atingir esse objetivo foram realizados testes em bancada utilizando os codecs de voz G729, G711, G723 e GSM analisando suas caracter?sticas de atraso e perda de pacotes. O trabalho apresenta resultados que indicam o efeito dos fen?menos de instabilidade das redes sem fio no desempenho do VoIP. Essas varia??es revelam altera??es significativas na qualidade da voz em fun??o do ambiente utilizado e da dist?ncia entre o emissor e receptor.