POI – Point of interconnect traffic
When you want to calculate the traffic what you should have first is
1.Total no of subscribes in MSC (Max at any given time in VLR)
2. Expected BHCA/sub -Busy hour call attempts per subsriber
3. Expected ACHT – Average call holding time
4. % of calls being routed to each POI .
Example:- Suppose one wants to serve 100K subs with BHCA of 3.5 and ACHT is 120 Secs.
Which means each subcriber at Busy Hour is going to make 3&1/2 call and each call on average is of 120 secs
So the traffic is
Now 8% of your Traffic goes to one POI then that traffic is 11666.67*(8/100)=933.33 Erlangs
Now cahnnels required to carry Traffic of 933.33 Erlnag, As per Erlang B table is with Blocking of 2% is 994
993/30(in case you are using only 30 Channels/E1)is around 33 E1s are required towards that POI.
I think this will clarify the query. Please mail me on firstname.lastname@example.org if any query on traffic. Its my pleasure to sort that out.