CALL CENTERS (CENTRES) - Faculty of Industrial Engineering and ...

for evaluating the consistency of the service provided to customers.
We analyze force and answer consistency algorithms based on three models: Erlang C, M/G/c,
and M/G/c with abandonments. Using two weeks of directory assistance (DA) field data, we
investigate how well these algorithms model the behavior of a real DA operator team. Although
the M/G/c model performs best, our analysis suggests that certain modifications to the simple
M/G/c model could significantly enhance its practical value.
41. Levy, Y., Johri S. Durinovic and R.A. Milito. Dynamic network call distribution with periodic
updates. Fundamental Role of Teletraffic in the Evolution of Telecommunications Networks.
Proceedings of the 14th International Teletraffic Congress, ITC-14, Elsevier, Amsterdam, The
Netherlands, 1994, 85–94.
Abstract. The ability to effectively distribute calls in the network to multiple customer sites
has become one of the major challenges for the intelligent network. The general goal is to make
effective use of available information to improve the load balancing across the sites and the overall
service level customers provide to their own clients. This paper introduces a new approach
consisting of two coupled algorithms: a traffic allocation algorithm and a call distribution algorithm.
The traffic allocation algorithm dynamically generates the proportion of global traffic
to be sent to each site in response to periodic updates of system state. The call distribution
algorithm converts this time varying allocation into a sequence of routing decisions. The paper
demonstrates that this easy-to-implement approach achieves superior performance even when
only a fraction of the offered traffic is controllable, provided that the update interval is not
excessively long.
Keywords: Dynamic network call distribution, Periodic updates, Multiple customer sites, Intelligent
network, Load balancing, Overall service level, Coupled algorithms, Traffic allocation
algorithm, Call distribution algorithm, Global traffic, System state, Time-varying allocation,
Routing decisions, Update interval, Traffic management
42. Perry, M. and A. Nilsson. Performance modeling of automatic call distributors: Operator services
staffing with heterogeneous positions. Fundamental Role of Teletraffic in the Evolution of
Telecommunications Networks. Proceeding of the 14th International Teletraffic Congress, ITC-
14. Elsevier, Amsterdam, The Netherlands, 1994, 1023–1032.
Abstract. The telephony industry has introduced a new generation of multi-purpose operator
positions, that with their associated automatic call distributor (ACD) allow operators to serve
both toll and assist (TA) and directory assistance (DA) calls from the same position. When all
operators can serve both TA and DA calls and all of the positions are multi-purpose, classical
Erlang-type queueing models can be used to calculate two important measures: the expected
waiting time for calls and the average operator occupancy. However when all of the positions
are not multi-purpose (i.e. the operators are a heterogeneous group: some can do both TA and
DA, some can do just TA and some can do just DA) the calculation of these two measures is
a new and challenging problem. In this paper, approximations for expected waiting times and
average occupancies are presented, and are shown, by comparison to simulation results, to be
quite accurate.
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