Staffing of Time-Varying Queues to Achieve Time-Stable Performance

Zohar Feldman (), Avishai Mandelbaum (), William A. Massey () and Ward Whitt ()
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Zohar Feldman: The William Davidson Faculty of Industrial Engineering and Management, Technion Institute of Technology, Haifa 32000, Israel
Avishai Mandelbaum: The William Davidson Faculty of Industrial Engineering and Management, Technion Institute of Technology, Haifa 32000, Israel
William A. Massey: Department of Operations Research and Financial Engineering, Princeton University, Princeton, New Jersey 08544
Ward Whitt: Department of Industrial Engineering and Operations Research, Columbia University, New York, New York 10027

Management Science, 2008, vol. 54, issue 2, 324-338

Abstract: This paper develops methods to determine appropriate staffing levels in call centers and other many-server queueing systems with time-varying arrival rates. The goal is to achieve targeted time-stable performance, even in the presence of significant time variation in the arrival rates. The main contribution is a flexible simulation-based iterative-staffing algorithm (ISA) for the M t /G/s t + G model--with nonhomogeneous Poisson arrival process (the M t ) and customer abandonment (the + G). For Markovian M t /M/s t + M special cases, the ISA is shown to converge. For that M t /M/s t + M model, simulation experiments show that the ISA yields time-stable delay probabilities across a wide range of target delay probabilities. With ISA, other performance measures--such as agent utilizations, abandonment probabilities, and average waiting times--are stable as well. The ISA staffing and performance agree closely with the modified-offered-load approximation, which was previously shown to be an effective staffing algorithm without customer abandonment. Although the ISA algorithm so far has only been extensively tested for M t /M/s t + M models, it can be applied much more generally--to M t /G/s t + G models and beyond.

Keywords: contact centers; call centers; staffing; nonstationary queues; queues with time-dependent arrival rates; many-server queues; capacity planning; queues with abandonment; time-varying Erlang models (search for similar items in EconPapers)
Date: 2008
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Citations: View citations in EconPapers (52)

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Persistent link: https://EconPapers.repec.org/RePEc:inm:ormnsc:v:54:y:2008:i:2:p:324-338

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