Enhancing VoWLAN service through adaptive voice coder

For the last decade, Voice Over IP (VoIP) has been a great concern leading to consider it as the ldquokilling applicationrdquo. Deploying such applications in the Wireless Local Area Networks (WLAN) is still in progress, and further investigations are needed. Unlike wired networks, wireless networks such as WLAN, have their own characteristics, which introduce many challenges that prohibit the support of real-time applications like VoIP. To support VoWLAN, it is commonly accepted that cross-layer cooperation is required. It involves an exchange of information between the MAC and the application layer aiming at better adapting the voice coder to the network conditions. In this paper, we propose to adapt the voice coder´s rate regarding the MAC layer feedbacks that reflect the network state in term of network load and physical rate. Simulation results show that compared to the case when using only G.711 coder, our crosslayer solution ensures high VoIP quality by maintaining low end-to-end delays and minimum PLR (Packet Loss Rate).