Description:
Erlang B calculator evaluates traffic, blocking and number of circuits. With two of these
parameters it estimates the third one. Moreover it distinguishes the offered traffic
(inflow) and the carried traffic (outflow):
a. Circuits: known the offered traffic and the blocking probability (GoS)
it calculates the circuits needed (or lines in a trunk group).
b. Blockage: known the circuits and the carried traffic it calculates the
blockage (blocked traffic and blocking probability).
c. Traffic: known the circuits and the blocking probability it calculates
the traffic it can carry.
If blocked calls are not rerouted, but they are retried, then the calculator uses the
extended Erlang B formula.
If arriving calls are not random, but they come from overflow, then you can use the
Wilkinson calculator.
If traffic is not blocked, but it waits in a queue, then you can use the
Erlang C calculator.
Instructions:
1. Select the calculator mode (circuits, blockage or traffic) depending on the
unknown parameters.
2. If blocked calls are retried, select "Retried calls" and
modify the retry probability, if necessary. If the blocked calls are rerouted, this will
not be necessary.
3. Enter the two known parameters.
4. Click "=" to evaluate the results; click "C" to
clear them; click "M+" to save them or "MR" to restore the saved ones.
In order to have the macros in Visual Basic, click on the "Excel" icon
tool.
Example:
For a traffic of 50 E and P.01 (1% of blocking probability), the circuits needed are 64.
Those circuits with 52 E carried have a workload that produces 1 E of blocked traffic. The
64 circuits with 10% of blocking have a capacity for 64.8 E of offered traffic. In a
system with 75% of blocked calls retried the offered traffic is reduced to 59.9 E.
Spanish:
Vea el índice en versión española.
http://personal.telefonica.terra.es/web/vr/erlang/eng/cerlangb.htm