Improving R-score of Adaptive VoIP codec in IEEE 802.16 networks

The IEEE 802.16 system called WiMAX (Worldwide Interoperability for Microwave Access) provides quality of service (QoS) of several types for different service. The WiMAX is expected to support QoS for real time application, such as Voice over IP (VoIP). In this paper, when network congestion occurs, the VoIP bit-rate needs to be adapted to achieve the best speech quality. We propose a new scheme called Adaptive VoIP Level Coding (AVLC). VoIP is sensitive to delay and loss. According to different network conditions such as varied modulation, packet delay, packet loss, and residual time slot, we use G.722.2 codec to adapt each connectionpsilas data rate. Simulation experiments are conducted to test the performance (network delay, packet loss, and R-score) of the proposed mechanisms. In result, we increase the R-score about 40% to 50%.