Voice over IP (VoIP) applications such as Skype, Google Talk, and FaceTime are promising technologies for providing cheaper voice calls to end users over extant networks. Wireless networks such as WiMAX and Wi-Fi focus on providing perfection of service for VoIP. However, there are numerous aspects that affect quality of voice connections over wireless networks [13]. The adoption of Voice over Wireless Local Area Network is on tremendous increase due its relief, non-invasive, economicexpansion, low maintenance cost, universal coverage and basic roaming capabilities. However, expansion Voice over Internet Protocol (VoIP) over Wireless Local Area Network (WLAN) is a challenging task for many network specialist and engineers. Voice codec is one of the most critical components of a VoIP system. In this project, we evaluate the performance analysis of various codecs such as G.711, G.723 and G.729 over Wi-Fi networks. NS2 Wi-Fi simulation models are designed. Performance metrics such as Mean Opinion Score (MOS), average end-to-end latency, and disconcert are evaluated and discussed [13].

IEEE 802.11 is the most popular standard for WLAN networks. It offers different physical transmission rates. This paper focuses on this multi transmission rate of 802.11 WLANs and its effect on speech quality. In non-adaptive systems, when the physical layer switches from a higher transmission rate to a lower one, different than the one that the VoIP flow needs, the switching may result in congestion, high delay and packet loss, and consequently speech quality degradation. However, there are some algorithms that adapt the transmission parameters according to the channel conditions. In this study we demonstrate how choosing parameter (different codec and packet size) can affect the voice quality, network delay and packet loss. Further, this study presents a comparison between adaptive and non-adaptive methods. The adaptive method has also been evaluated for different congestion level from perceived speech quality point of view.

Voice over IP (VoIP) applications such as Skype, Google Talk, and FaceTime are promising technologies for providing cheaper voice calls to end users over extant networks. Wireless networks such as WiMAX and Wi-Fi focus on providing perfection of service for VoIP. However, there are numerous aspects that affect quality of voice connections over wireless networks [13]. The adoption of Voice over Wireless Local Area Network is on tremendous increase due its relief, non-invasive, economicexpansion, low maintenance cost, universal coverage and basic roaming capabilities. However, expansion Voice over Internet Protocol (VoIP) over Wireless Local Area Network (WLAN) is a challenging task for many network specialist and engineers. Voice codec is one of the most critical components of a VoIP system. In this project, we evaluate the performance analysis of various codecs such as G.711, G.723 and G.729 over Wi-Fi networks. NS2 Wi-Fi simulation models are designed. Performance metrics such as Mean Opinion Score (MOS), average end-to-end latency, and disconcert are evaluated and discussed [13].

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