I do not think you got my point. It is quite clear, that during conversation it is close to zero. Using G711 even DTMF may go inband. However it is not zero in given period of time. Read carefully – having 100k subscribers there is a real bandwidth consumption on the line during call setup/clearing, because it is not separated from RTP. So, some of the calls were set up, some are just tearing down and some other are in the process of setting up. In total it generates traffic on the line. In such a case it is not zero if you look carefully at the scale of the traffic. Even if it is 1, or 2 percent it is still some bandwidth consumption. And that’s what I am looking for.
If you have to calculate system capacity having BHCA there is for sure relation with SIP messages exchange. Because BHCA gives you information on how many people TRIED to set up the call during one hour, and not how many succeeded. You may try to call particular person 5-10 times during busy hour and have no conversation at all, because busy signal, or he/she is out of the office, or simply cannot pick up the call. Comparing to SIP network – you will generate fair amount of signaling traffic and no RTP.
So, thank you for response, but answer is not that simple for sure 🙂