ISSN 0032-9460, Problems of Information Transmission, 2013, Vol. 49, No. 1, pp. 58–72.
Pleiades Publishing, Inc., 2013.
Original Russian Text
S.A. Dudin, O.S. Dudina, 2013, published in Problemy Peredachi Informatsii, 2013, Vol. 49, No. 1, pp. 66–82.
COMMUNICATION NETWORK THEORY
Help Desk Center Operating Model
as a Two-Phase Queueing System
S. A. Dudin and O. S. Dudina
Belarusian State University, Minsk, Belarus
Received March 3, 2012; in ﬁnal form, October 5, 2012
Abstract—We consider a two-phase queueing system with a Markovian arrival ﬂow as an op-
erating model for a help desk center. The ﬁrst phase is a multiserver system with a ﬁnite buﬀer
and impatient customers. After getting service in the ﬁrst phase, a customer either enters the
second phase with an inﬁnite buﬀer or quits the system. Service times at the ﬁrst and second
stages have phase-type distributions with diﬀerent parameters. We obtain an existence condi-
tion for a stationary regime of the system. An algorithm for computing stationary probabilities
and basic performance characteristics of the system is presented. Laplace–Stieltjes transforms
for the distributions of sojourn and waiting times in the ﬁrst and second phases are found. Re-
sults of numerical experiments are presented. Optimization problem for the system operation
is solved numerically.
A help desk center, or information service call center, provides a wide range of information
services and technical support for customers using diversiﬁed hard- and software. Development of
information technologies have lead to an extensive spread of help desk centers in various spheres
of social life.
An example of a help desk center is information and technical support service of Internet
providers. In the case of problems with Internet connection settings, a customer may address
to an information support center of his provider. Usually, information support service has a two-
level structure. At the ﬁrst stage, a customer makes a call to a company call center and waits for
an operator reply (operators can not only receive customers’ requests but also make other func-
tions, for instance, advise potential customers). The operator registers a request and, if possible,
provides assistance to the customer. For example, if a service was disabled because of nonpayment,
the operator may point out the necessity to repay a dept for the service to be resumed. In a case
where the call center operator cannot decide an issue on his own, he asks the customer to wait for
a reply of a specialist (system administrator, engineer, technician). At the second stage, specialists
of the support service receive requests from operators, call back to customers, and help them to
resolve their problems.
In optimizing the operation of a help desk center there arises a nontrivial problem of ﬁnding the
optimum number of call center operators and specialists necessary for servicing customers with a
given quality level. If the number of operators and/or specialists is too large, the company incurs
considerable upkeep costs. On the other hand, deﬁciency in the number of operators and specialists
Supported in part by the Belarusian Republican Foundation for Fundamental Research, project no.