most important is one which helps in calculating the amount of traffic from number of calls and holding time is:
a = λh.
λ=number of call connections
h=mean holding time
from this you will find the amount of traffic being catered by current network. If you think keeping in view the traffic that the resources are not sufficient for that amount of traffic then you can use:
P(b)=(a^n/n!)/summation i=0-n (a^i/i!)
Pb is the probability of blocking
n is the number of resources such as servers or circuits in a group
a = λh is the total amount of traffic offered in erlangs.
From all this info you may find the number of resources (E32 interface cards) for any traffic and blocking. All other equipment will be expanded with respect to the expansion of E32 rsources.
Hope this give sufficient info for the query. If anyone has more info or if im wrong at any point then then plz share.