STEM help / Data dialogs

Transformation / Erlang B formula

An Erlang B formula transformation may be selected from the Type menu in the Input and Transformation dialog. The Erlang B formula is used to determine the number of channels required to support a given level of traffic with a given probability of blocking – the Grade of Service (GOS).

These inputs are accessed via the Input and Transformation dialog.

Output Unit

Select the output unit that you want to use from the drop-down list box, or define your own. The selection has no effect on the model but is used in results graphs.

Default: none.

Features See Multiplier Transformation, Transformations.

Multiplier (2)

Multiplies the Input of a Transformation to calculate its Output.

Default: Constant {1.0}.

Features See Multiplier Transformation, Transformations.

Erlang B formula

Grade of Service

The grade of service parameter required in the Erlang B formula. This represents the probability of blocking on a Service, typically of the order of 0.001 for a fixed network.

Default: 0.0. This must be set to a non-zero value.

Features See Erlang B formula, Erlang B Formula Transformation.

Sites (3)

The number of sites (or links) across which traffic, and hence capacity, is distributed, which can be defined directly as a time series, or as a reference to a separate Location or Transformation element.

Default: Location (<none>). Demand is treated as one single bundle.

Features See Erlang B formula, Transformations.

Input

Identifies an element as a source of demand for a Transformation; together with a Basis, which specifies the particular result, associated with that element, which defines the size of that Input in any year. Expression Transformations have several inputs, called Input 1, Input 2, and so on.

Default: Resource (<none>, Installed Capacity). For an Erlang B Formula transformation, Service (<none>, Busy Hour Traffic). For a Time Factor transformation, Transformation (<none>).

Features See Transformations.

 

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