VoIP Voice and Fax Signal Processing

11.8 BIT RATE WITH RTCP, RTCP-XR, AND SIGNALING

RTCP is the RTP control protocol [Schulzrinne et al. (2003)]. RTCP packets are used to send the packet reports at regular intervals. The bit rate from RTCP is controlled to less than 5% of the RTP bit rate listed in the previous sections. In practical systems, users are controlling RTCP bit rate to 1% to 3%. RTCP-XR is the RTCP extended reports [Friedman et al. (2003)]. It is used mainly for sending voice quality monitoring parameters. These packets are generated usually once in 256 basic frames of RTP. The bit rate contribution of RTCP-XR is very low, less than 0.5%, which can be accounted for as part of the RTCP 5% allocation. Signaling packets are generated while establishing the calls, tearing down the calls, and establishing the call features. In the initial and final stages of the calls, no voice packets occur in the call. Hence, signaling packets can reuse part of the voice packet bit rate. In steady state, signaling activity reduces except for any new call feature activity. As an approximation, accounting for about 10% of voice packets bit rate can take care of RTCP, RTCP-XR, and signaling bit rate requirements.