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Encyclopedia > Engset calculation

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The Engset calculation was named after its developer, T. O. Engset, who developed it to determine the probability of congestion occurring within a circuit group. The level of congestion can be used to determine a network's performance as it directly relates to grade of service. The formula requires that the user knows the expected peak traffic, the number of sources (callers) and the number of circuits in the network. Full name Tore Olaus Engset born 1865­, died 1943. ... In telecommunication, the term grade of service (GOS) has the following meanings: The probability of a call being blocked or delayed for more than a specified interval, expressed as a decimal fraction. ...


Engset's equation is similar to the Erlang-B formula; however it contains one major difference: Erlang's equation assumes an infinite source of calls and Engset specifies a finite number of calls [1]. Thus Engset's equation should be used when the source population is small (say less than 200 customers). The Erlang distribution is a probability distribution developed by A. K. Erlang to predict waiting times in queueing systems, particularly in the case of telephone traffic engineering. ...


Like Erlang's equations, Engset's formula requires recursion to solve for the blocking probability. To determine the probability of congestion, the user must first determine an initial estimate. This initial estimate is substituted into the equation and the equation then is solved. The answer to this initial calculation is then substituted back into the equation, resulting in a new answer which is again substituted. This iterative process continues until the equation converges to the correct answer [1, 2]. Iteration is the repetition of a process, typically within a computer program. ...


Engset's equation follows [1]:

where

A = offered traffic intensity in erlangs, from all sources
S = number of sources of traffic
N = number of circuits in group
P(b) = probability of blocking or congestion

References

[1] Parkinson R., Traffic Engineering Techniques in Telecommunications, Infotel Systems Inc [1] (http://www.tarrani.net/mike/docs/TrafficEngineering.pdf). Last accessed 13 February 2005 February 13 is the 44th day of the year in the Gregorian Calendar. ... 2005 is a common year starting on Saturday of the Gregorian calendar. ...


[2] ITU-T Study Group 2, Teletraffic Engineering Handbook [2] (http://www.com.dtu.dk/teletraffic/handbook/telenook.pdf). Last accessed 13 February 2005 February 13 is the 44th day of the year in the Gregorian Calendar. ... 2005 is a common year starting on Saturday of the Gregorian calendar. ...


  Results from FactBites:
 
Erlang unit (446 words)
In the traffic calculation, one Erlang implies a single resource in continuous use (or two channels at fifty percent use, and so on, pro rata).
It might be used to measure traffic on a T-1 or E-1 line, to determine how many 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 data channels.
Engset formula ( named after 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.
Engset calculation - Wikipedia, the free encyclopedia (394 words)
Engset, who created it to determine the probability of congestion occurring within a circuit group.
Engset's equation is similar to the Erlang-B formula; however it contains one major difference: Erlang's equation assumes an infinite source of calls and Engset specifies a finite number of callers [1].
The answer to this initial calculation is then substituted back into the equation, resulting in a new answer which is again substituted.
  More results at FactBites »


 

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