PSTN Conference Call Profiler

Is there out there a model of how to plan capacity for Voice Conference?

I’m looking for a model for the general behavior of voice conferences and arrival rate of calls & how to derive the capacity needed for circuits, etc. We generally know that conferences are most likely to start on the hour or on the 1/2 hour. How would a 5 calls/sec arrival rate translates to number of calls at peak time? Or will this arrival rate accommodate a population for ‘xxx’ subscribers at 11:00am? How timezone will play into this?
I assume that callers will be from different time-zones, here GMT should probably be the reference point.

Any thoughts?

A. Zahavi