Andrew M. Ross

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Various topics on queues:

How important are telecommunications?

A presentation tip

I investigate the properties of queueing systems where the arrival rate is non-homogeneous. The two primary examples of this are when it changes according to the time-of-day, and when it is subject to forecasting error. Two common examples are telephone call centers (such as emergency 9-1-1) and modem banks for internet access. My advisor was Prof. Shanthikumar.

In queueing theory notation, call centers are described as Mt/G/c (or Mt/G/k or Mt/G/s) systems. The phrase "Erlang delay system" is also used. When we want to take into account the fact that a limited number of people can be on hold, we write Mt/G/c/c+r (or Mt/G/k/k+r or Mt/G/s/s+r) to denote those extra phone lines.

Wouldn't it be nice if there was a standard way to describe queueing systems that was search-engine friendly? Search engines don't like terms that have lots of slashes in them, like M/M/s. Also, people use different terms for the number of servers, which means that to do a web search, you have to try it once for each possiblity. Ick.

Modem banks are described as Mt/G/c/c+0 systems, also called Erlang loss systems. If all the modems are busy when a call arrives, it gets a busy signal instead of being put on hold, as it would at a call center.