Teletraffic engineering, telecommunications traffic engineering, or just traffic engineering when in context, is the application of transportation traffic engineering theory to

telecommunications Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...

. Teletraffic engineers use their knowledge of statistics including

queuing theory Queueing theory is the mathematical study of waiting lines, or queues. A queueing model is constructed so that queue lengths and waiting time can be predicted. Queueing theory is generally considered a branch of operations research because the ...

, the nature of traffic, their practical models, their measurements and

simulations A simulation is the imitation of the operation of a real-world process or system over time. Simulations require the use of models; the model represents the key characteristics or behaviors of the selected system or process, whereas the s ...

to make predictions and to plan telecommunication networks such as a

telephone network A telephone network is a telecommunications network that connects telephones, which allows telephone calls between two or more parties, as well as newer features such as fax and internet. The idea was revolutionized in the 1920s, as more and mor ...

or the

Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...

. These tools and knowledge help provide reliable service at lower cost. The field was created by the work of

A. K. Erlang Agner Krarup Erlang (1 January 1878 – 3 February 1929) was a Denmark, Danish mathematician, statistician and engineer, who invented the fields of teletraffic engineering, traffic engineering and queueing theory. By the time of his relatively ...

for circuit-switched networks but is applicable to

packet-switched network In telecommunications, packet switching is a method of grouping data into '' packets'' that are transmitted over a digital network. Packets are made of a header and a payload. Data in the header is used by networking hardware to direct the pack ...

s, as they both exhibit Markovian properties, and can hence be modeled by e.g. a Poisson arrival process. The crucial observation in traffic engineering is that in large systems the law of large numbers can be used to make the aggregate properties of a system over a long period of time much more predictable than the behaviour of individual parts of the system.

In PSTN architectures

The measurement of traffic in a public switched telephone network (PSTN) allows network operators to determine and maintain the

quality of service Quality of service (QoS) is the description or measurement of the overall performance of a service, such as a telephony or computer network, or a cloud computing service, particularly the performance seen by the users of the network. To quantitat ...

(QoS) and in particular the

grade of service In telecommunication engineering, and in particular teletraffic engineering, the quality of voice service is specified by two measures: the grade of service (GoS) and the quality of service (QoS). Grade of service is the probability of a call in a ...

(GoS) that they promise their subscribers. The performance of a network depends on whether all origin-destination pairs are receiving a satisfactory service. Networks are handled as: *loss systems, where calls that cannot be handled are given equipment busy tone, or *queuing systems, where calls that cannot be handled immediately are queued. Congestion is defined as the situation when exchanges or circuit groups are inundated with calls and are unable to serve all the subscribers. Special attention must be given to ensure that such high loss situations do not arise. To help determine the probability of congestion occurring, operators should use the

Erlang formula The erlang (symbol E) is a dimensionless unit that is used in telephony as a measure of offered load or carried load on service-providing elements such as telephone circuits or telephone switching equipment. A single cord circuit has the capaci ...

s or the

Engset calculation In queueing theory, the Engset formula is used to determine the blocking probability of an M/M/c/c/N queue (in Kendall's notation). The formula is named after its developer, T. O. Engset. Example application Consider a fleet of c vehicles and N ...

. Exchanges in the PSTN make use of

trunking In telecommunications, trunking is a technology for providing network access to multiple clients simultaneously by sharing a set of circuits, carriers, channels, or frequencies, instead of providing individual circuits or channels for each cli ...

concepts to help minimize the cost of the equipment to the operator. Modern switches generally have full availability and do not make use of grading concepts. Overflow systems make use of alternative routing circuit groups or paths to transfer excess traffic and thereby reduce the possibility of congestion. A very important component in PSTNs is the SS7 network used to route signalling traffic. As a supporting network, it carries all the signalling messages necessary to set up, break down or provide extra services. The signalling enables the PSTN to control the manner in which traffic is routed from one location to another. Transmission and switching of calls is performed using the principle of time-division multiplexing (TDM). TDM allows multiple calls to be transmitted along the same physical path, reducing the cost of infrastructure.

In call centers

A good example of the use of teletraffic theory in practice is in the design and management of a call center. Call centers use teletraffic theory to increase the efficiency of their services and overall profitability through calculating how many operators are really needed at each time of the day. Queueing systems used in call centers have been studied as a science. For example, completed calls are put on hold and queued until they can be served by an operator. If callers are made to wait too long, they may lose patience and default from the queue (hang up), resulting in no service being provided.

In broadband networks

Teletraffic engineering is a well-understood discipline in the traditional voice network, where traffic patterns are established, growth rates can be predicted, and vast amounts of detailed historical data are available for analysis. However, in modern broadband networks, the teletraffic engineering methodologies used for voice networks are inappropriate.What is the role of teletraffic engineering in broadband networks? by Jones Kalunga
cnx.org

Long-tail traffic

Of great importance is the possibility that extremely infrequent occurrences are more likely than anticipated. This situation is known as

long-tail traffic A long-tailed or heavy-tailed probability distribution is one that assigns relatively high probabilities to regions far from the mean or median. A more formal mathematical definition is given below. In the context of teletraffic engineering a number ...

. In some designs, the network might be required to withstand the unanticipated traffic.

Teletraffic economics and forecasting

As mentioned in the introduction, the purpose of teletraffic theory is to reduce cost in telecommunications networks. An important tool in achieving this goal is

forecasting Forecasting is the process of making predictions based on past and present data. Later these can be compared (resolved) against what happens. For example, a company might estimate their revenue in the next year, then compare it against the actual ...

. Forecasting allows network operators to calculate the potential cost of a new network / service for a given QoS during the planning and design stage, thereby ensuring that costs are kept to a minimum. An important method used in forecasting is

simulation A simulation is the imitation of the operation of a real-world process or system over time. Simulations require the use of models; the model represents the key characteristics or behaviors of the selected system or process, whereas the s ...

, which is described as the most common quantitative modelling technique in use today. An important reason for this is that computing power has become far more accessible, making simulation the preferred analytical method for problems that are not easily solved mathematically. As in any business environment, network operators must charge

tariffs A tariff is a tax imposed by the government of a country or by a supranational union on imports or exports of goods. Besides being a source of revenue for the government, import duties can also be a form of regulation of foreign trade and po ...

for their services. These charges must be balanced with the supplied QoS. When operators supply services internationally, this is described as

trade in services Trade in Services refers to the sale and delivery of an intangible product, called a service, between a producer and consumer. Trade in services that takes place between a producer and consumer that are, in legal terms, based in different countrie ...

and is governed by the

General Agreement on Trade in Services The General Agreement on Trade in Services (GATS) is a treaty of the World Trade Organization (WTO) which entered into force in January 1995 as a result of the Uruguay Round negotiations. The treaty was created to extend the multilateral trading sy ...

(GATS).

References

* "Deploying IP and MPLS QoS for Multiservice Networks: Theory and Practice" by John Evans, Clarence Filsfils (Morgan Kaufmann, 2007, ) * V. B. Iversen, Teletraffic Engineering handbook,

* M. Zukerman, Introduction to Queueing Theory and Stochastic Teletraffic Models
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{{DEFAULTSORT:Teletraffic Engineering Teletraffic, Queueing theory Broadband Telecommunications de:Traffic Engineering ja:通信トラヒック工学