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The Extended Erlang B Traffic Model

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A derivation of Erlang's original work, the Extended Erlang B Traffic Model is an analytical model for calculating call blocking. It makes the following assumptions:

 

Calls are presented randomly to a trunk group (Poisson arrivals).
Call times are fixed or are exponentially distributed.

 

Unlike the Erlang B Traffic Model, the Extended Erlang B Traffic Model takes into account the extra traffic offered to a trunk group caused by retries; that is, calls that are immediately redialled because they were blocked.

 

This traffic model may be applied to situations in which no overflow facilities exist.

 

See also

 

The three variables

Recall factor