Do you have a question? Post it now! No Registration Necessary. Now with pictures!
June 30, 2005, 4:58 am
rate this thread
the modules for Erlang B/C calculations are now available at
The Erlang B model allows dimensioning the number of servers in a
M/M/S/0/inf model (Kendall notation), which basically has S servers
whose service time has negative-exponential probability density, in
which there are infinite potential users arriving with
negative-exponential time probability density, and which are dropped if
all S servers are busy (there is no "wait queue", aka "wait line").
This model is widely used in telecommunications, especially to
dimension telephone lines/channels (e.g. in mobile networks, where you
have to allocate channels in a radio base station), because of the
absence of a "wait queue".
The Erlang C model allows dimensioning the number of servers in a
M/M/S/inf/inf model; the difference with respect the Erlang B model is
that there is an infinite "wait queue", that is when users find all S
servers busy, the wait in an ordered queue until they can access one of
them. This can be used to dimension call-centres resources, because
call-centres usually support a wait queue; note that this is a model
that is somehow different from reality, because in the model a user is
supposed to have infinite patience :)
Both modules have a function-oriented interface. The Erlang C model has
a lot of functions with awkward names, so I'm planning to divide them
in groups under sub-modules - suggestions welcome!
The former has already been registered under Math::Telephony::ErlangB;
I asked to register the latter under Math::Telephony::ErlangC.
Flavio (frodo72 in Perl Monks).