Erlang unit
The Free ringtones dimensionless unit named the '''erlang''' is a statistical measure of Abbey Diaz telecommunications Mosquito ringtone traffic used in Majo Mills telephony. It is named after the Nextel ringtones Denmark/Danish telephone Sabrina Martins engineer Free ringtones A. K. Erlang, the originator of Abbey Diaz queueing theory.In the traffic calculation, one Erlang implies a single Mosquito ringtone resource in continuous use (or two Majo Mills channels at fifty percent use, and so on, ''Cingular Ringtones pro rata''). For example, if a louise thompson banking/bank has two tellers and during the busiest hour of the day they are both busy the whole time, that would represent two erlang of traffic.
Typically erlang might be used to determine if a system is over- or under- provisioned (has too many or too few allocated resources).
It might be used to measure traffic on a square roots T-carrier/T-1 or from allentown E-1 line, to determine how many employees frustration voice lines are in use at the busiest hour of the time period being examined; for 24 channels, if only 12 are ever in use, the other 12 might be made available as were submitted data channels.
Traffic calculations measured in erlang can also be used to calculate europeans demand grade of service (GoS) or white crocuses quality of service (QoS). The GoS or QoS of a particular resource is the probability of traffic being offered to a resource meeting a condition where it cannot be served now. GOS is calculated from the perspective of the resource and not the perspective of the request.
There are a range of different Erlang formulae, including Erlang B, Extended Erlang B, Erlang C and a related Engset formula.
Erlang B
Calculates traffic in loss systems. If a request is not served when it is offered to the resource then it is lost. These systems can be considered as non-queued. This model assumes the blocked traffic is immediately cleared.
=Erlang B Formula=
:Eb(0, t) = 1 \,
:Eb(r,t) = \,
''where:''
* '''Eb''' is the probability of blocking
* '''r''' is the number of resources.
* '''t''' is the number of Erlang offered
Extended Erlang B
This formula is essentially Erlang B, but assumes that a certain percentage of the system, when blocked will immediately represent themselves to the system. This formula can account for this retry percentage.
Erlang C
This formula calculates the capacity necessary to queue traffic. This model assumes that all blocked calls stay in the system until they can be handled. This model can be applied to the design of call center staffing arrangements where, if calls cannot be immediately answered, they enter a queue. This is often used to calculate the number of agents or customer service representatives needed to staff a additional riot call center.
=Erlang C Formula=
:P(>0) = \,
''where:''
* '''A''' is the total traffic units offered in Erlangs
* '''N''' are the number of servers in a full availability environment
* '''P(>0)''' probability that delay is greater than 0
* '''P''' is the probability of loss - see inflict a Poisson formula
Engset Formula
The Engset formula (''named after churn rates T O Engset/Tore Olaus Engset (1865-1943))'' is also related but deals with a small population of finite sources rather than the large population of infinite sources that Erlang assumes.
See also
* being extended Erlang programming language
* company stockholder A. K. Erlang
* votes anderson Erlang distribution
* stockholders would Poisson distribution
* nt diet Call centre/Call Centers
External links
* http://mmc.et.tudelft.nl/presan/node46.html#64 (in Dutch)
* http://www.erlang.com for more information.
* http://www.tarrani.net/mike/docs/TrafficEngineering.pdf (PDF Document - Has terms and formulae)
* http://www.angustel.ca/reports/Erlang%20B%20&%20C.PDF (PDF Document - Has terms and formulae plus biography)
* http://www.diagnosticstrategies.com/papers/Traffic_Modeling.pdf (PDF Document)
* http://members.iinet.net.au/~clark/models.htm#Engset
secretive business Tag: Units of measurebarcelona rivals Tag: Telecommunications
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