OR Spectrum

, Volume 26, Issue 3, pp 353–376 | Cite as

The impact of retrials on call center performance

  • Salah Aguir
  • Fikri Karaesmen
  • O.  Zeynep Akşin
  • Fabrice Chauvet
Article

Abstract.

This paper models a call center as a Markovian queue with multiple servers, where customer balking, impatience, and retrials are modeled explicitly. The resulting queue is analyzed both in a stationary and non-stationary setting. For the stationary setting a fluid approximation is proposed, which overcomes the computational burden of the continuous time markov chain analysis, and which is shown to provide an accurate representation of the system for large call centers with high system load. An insensitivity property of the retrial rate to key system parameters is established. The fluid approximation is shown to work equally well for the non-stationary setting with time varying arrival rates. Using the fluid approximation, the paper explores the retrial phenomenon for a real call center. The model is used to estimate the real arrival rates based on demand data where retrials cannot be distinguished from first time calls. This is a common problem encountered in call centers. Through numerical examples, it is shown that disregarding the retrial phenomenon in call centers can lead to huge distortions in subsequent forecasting and staffing analysis.

Keywords:

Call centers Multi-server queues Retrials 

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Copyright information

© Springer-Verlag Berlin/Heidelberg 2004

Authors and Affiliations

  • Salah Aguir
    • 1
  • Fikri Karaesmen
    • 2
  • O.  Zeynep Akşin
    • 3
  • Fabrice Chauvet
    • 4
  1. 1.Laboratoire Génie IndustrielEcole Centrale ParisChatenay-Malabry CedexFrance
  2. 2.Department of Industrial EngineeringKoç UniversitySariyer,IstanbulTurkey
  3. 3.Graduate School of BusinessKoç UniversitySariyer, IstanbulTurkey
  4. 4.Bouygues Telecom R&DVelizy CedexFrance

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