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The dimensionless unit named the Erlang is a statistical measure of telecommunications traffic used in telephony. It is named after the Danish telephone engineer A. K. Erlang, the originator of traffic engineering and queueing theory. In the physical sciences, a dimensionless number (or more precisely, a number with the dimensions of 1) is a quantity which describes a certain physical system and which is a pure number without any physical units; it does not change if one alters ones system of units of measurement...
BlackBerry 7100t Telecommunication refers to the communication of information at a distance. ...
Interstate 80, a freeway in California with many lanes and heavy traffic. ...
In telecommunication, Telephony encompasses the general use of equipment to provide voice communication over distances. ...
Look up engineer in Wiktionary, the free dictionary. ...
Agner Krarup Erlang (January 1, 1878–February 3, 1929) was a Danish mathematician, statistician, and engineer who invented the fields of queueing theory and traffic engineering. ...
For another meaning of the term traffic engineering, please see transport traffic engineering. ...
Queueing theory (also commonly spelled queuing theory) is the mathematical study of waiting lines (or queues). ...
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). For example, if a bank has two tellers and they are both busy the whole time, that would represent two Erlangs of traffic. Resources comprise the base material for an activity or industry: factors of production, the economics term human capital, human resources (HR) and innovation natural resources resource (computer science) resource (Web) resource (Windows) resource (Macintosh) resource (political) resource (project management) Resource Distribution, human influence and the effects of trade. ...
Channel, in communications (sometimes called communications channel), refers to the medium through which information is transmitted from a sender (or transmitter) to a receiver. ...
For other uses, see Bank (disambiguation). ...
The traffic measured in Erlangs is used to determine if a system is over- or under-provisioned (has too many or too few resources allocated).
The traffic measured over many busy hours might be used for a T1 or E1 circuit group to determine how many voice lines are in use at the busiest hours. For example, if no more than 12 out of 24 channels are ever in use at any given time, the other 12 might be made available as data channels. Two Network Interface Units, one with a single card, the other with two In telecommunications, T-carrier is the generic designator for any of several digitally multiplexed telecommunications carrier systems originally developed by Bell Labs and used in North America and Japan. ...
In digital telecommunications, where a single physical wire can be used to carry many simultaneous voice conversations, worldwide standards have been created and deployed. ...
Human voice consists of sound made by a person using the vocal folds for talking, singing, laughing, screaming or crying. ...
Data is the plural of datum. ...
Traffic measured in Erlangs is used to calculate grade of service (GOS) or quality of service (QoS). // Introduction In telecommunication, the quality of voice service is specified by two measures: The GOS (grade of service) and the QoS (quality of service). ...
In the fields of packet-switched networks and computer networking, the traffic engineering term Quality of Service (QoS, pronounced Que-Oh-Es) refers to the probability of the telecommunication network meeting a given traffic contract, or in many cases is used informally to refer to the probability of a packet...
There are a range of different Erlang formulae, including Erlang B, Extended Erlang B, Erlang C and a related Engset formula to calculate GOS.
Erlang B
Calculates blocking probability in a loss system. If a request is not served immediately when it tries to use a resource, then the request is aborted. These systems are therefore not queued. The formula assumes the blocked traffic is immediately cleared.
Erlang B formula   where: - Eb is the probability of blocking
- r is the number of resources (eg. servers or circuits in a group).
- t is the amount of traffic offered in Erlangs.
Erlang B formula works for loss systems, thus it applies to telephony systems both for fixed and mobile networks due to their real time nature where they simply do not (and are not intended to) provide traffic buffering.
Extended Erlang B This formula is essentially Erlang B, but assumes that a certain percentage of calls to the system will immediately re-present themselves to the system after being blocked. This formula accounts for this re-try percentage.
Erlang C This formula calculates the probability of queueing offered traffic. This formula assumes that blocked calls stay in the system until they can be handled. This formula can be applied to the design of call centre staffing arrangements, because when calls cannot be immediately answered, they enter a queue. The formula is used to determine the number of agents or customer service representatives needed to staff a call centre. A call centre (Commonwealth English) or call center (American English) is a centralized office used for the purpose of receiving and transmitting a large volume of requests by telephone. ...
Erlang C formula  where: - A is the total traffic units offered in Erlangs
- N is 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 Poisson distribution
Erlang C formula works for queueing systems thus it applies to packet data networks (such as internet, etc) due to their non real-time nature. Delay time generally acceptable for packet transmission allows the incorporation of data buffer along with routers. The buffer provides queuing for the data traffic. In probability theory and statistics, the Poisson distribution is a discrete probability distribution. ...
Engset formula The 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. This article is one of a group being considered for deletion in accordance with Wikipedias deletion policy. ...
Full name Tore Olaus Engset born 1865, died 1943. ...
See also Agner Krarup Erlang (January 1, 1878–February 3, 1929) was a Danish mathematician, statistician, and engineer who invented the fields of queueing theory and traffic engineering. ...
A call centre (Commonwealth English) or call center (American English) is a centralized office used for the purpose of receiving and transmitting a large volume of requests by telephone. ...
This article is one of a group being considered for deletion in accordance with Wikipedias deletion policy. ...
Erlang is a general-purpose concurrent programming language and runtime system. ...
The Erlang distribution is a continuous probability distribution with wide applicability primarily due to its relation to the exponential and Gamma distributions. ...
In probability theory and statistics, the Poisson distribution is a discrete probability distribution. ...
In Telecommunication engineering and Teletraffic theory, a Traffic Model is commonly referred to as a Traffic Mix. ...
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