Erlang Calculators
The Erlang traffic models were established by A.K.
Erlang, a Danish scientist who is credited with much of the early work in
telephone traffic design.
Erlang calculators are used throughout the world to carry out a
variety of statistical estimations associated with telecommunications systems
and call centers.
There are several variants of Erlang calculators for specific purposes
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Erlang C
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Call Centers, help
desks, checkout queues, where customers can wait in a queue.
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Extended
Erlang B
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Used
by telephone system designers to estimate the number of lines required for
PSTN connections and takes into account the additional traffic load caused
by blocked callers immediately trying to call again if their calls are
blocked.
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Erlang
B
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Us
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The Erlang C calculator models the
performance of systems which incorporate queuing (rather than a caller simply
getting a busy signal and hanging up). Queuing applications include switchboard
operators, call center agents and helpdesks. However the same calculations also
apply to supermarket checkout queues, toll booths etc.
The Erlang C model makes the following
assumptions -
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Calls
are offered randomly in a queue (Poisson arrivals)
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Users
wait if they find the system busy (no account is made of the effect of
abandoned calls)
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Service
times are exponential
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Users
are served in the order of their arrival
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Users
are directed to the first-available agent
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Queue
sizes are unlimited
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There
are not dramatic variations in call volumes within the period being
calculated
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