Voice Over IP

PACKET SIZE, BUFFER SIZE, LOSS, AND LATENCY

The VoIP designer must pay attention to buffer sizes, packet sizes, and the packet loss rate. The larger the packet loss, the worse the audio quality will be at the receiver. On the other hand, large packet sizes increase the delay and so do large buffers. To see why, let us examine a simple G.711 64 kbit/s voice signal.

First, consider the loss of user traffic. The size of the packet is quite important for speech because of the concept of packet length (the duration of the packet on the channel). Packet length is a function of the number of user bits in the packet, and the coding rate of the signal (for example, 64 kbit/s). Studies reveal that losing traffic that is around 32–64 ms (for G.711 traffic) ...