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TopVoice codec generally provide a compression capability to save network bandwidth. Currently, there are various types of audio codecs available for voice applications. The simplest and most widely used codecs are G.711, G.723 and G.729 (Nguyen, Yegenoglu, Sciuto, & Subbarayan, 2001). The simplest encoder scheme is G.711 (64 kb/s). G.711 is the sample base which uses the Pulse Code Modulation (PCM). The acceptable packet loss factor of G.711 is up to 0.928%. In this paper, we consider a simulation scenario to study the performance of G.711, G.723, and G.729.
In reference (Zeadally, Siddiqui, & Kubher, 2004), the authors have studied a large scale WLAN system with about 2000 nodes and have presented most comprehensive trace of network activity. This study can help understand usage patterns in WLANs which are critical for those who develop, deploy, and manage wireless technologies as well as those who develop systems and application software for wireless networks (Salah & Alkhoraidly, 2006; Chou, 2007; Walsh & Kuhn, 2005; Huijie & Xiaokang, 2005; Van de Capelle, Van Lil, Theunis, Potemans, & Teughels, 2001; Baratvand, Tabandeh, Behboodi, & Ahmadi, 2008).
Table 1 lists the key researchers and their main contributions in the performance studies of VoIP over wired and wireless networks.