Re: Erlang B
Erlang is a standard unit to represent the traffic in a system. It can be explained as below :
One Erlang of traffic means that a switch is occupied for a given period of observation.
Consider the observation period for occupancy of a switch is 60 sec ( which is standard ).
Then , the offered load to the system can be calculated in terms of Erlang as :
A= Q * T / 60
where Q = call arrival rate ( calls/min)
T = call holding time (minutes per call)
So, if say for an example .... in a system maximum calls per hour is 3000 (i.e. the total call attempts made by the subscribers or it can be said the total number of active subscribers in the system)
and the average calling time is1.76 min (i.e. each subscriber has occupied the switch for 1.76 mins on an average)
then load on system in terms of Erlang is calculated as :
A = 3000*1.76/60
= 88 Erlang...
Now , when u know the blocking probability and the number of channels of the system u can easily find out the offered load by just looking into the appendix 1.1 given in book MOBILE CELLULAR TELECOMMUNICATIONS analog and digital systems - By
WILLIAM C.Y. LEE
which is available at following link too :
https://www.amazon.ca/Mobile-Cellular-Telecommunications-Systems-William/dp/0070370303
For finding out the offered load on a system you just require blocking probability and no. of channels allotted to the system or you just require the no. of active subscribers(i.e. total call attempts made) and average call holding time....
I HOPE U HAVE NOW UNDERSTOOD WHAT DOES IT MEANS ....