# Designing a Call Center with Impatient Customers

@article{Garnett2002DesigningAC, title={Designing a Call Center with Impatient Customers}, author={O. Garnett and Avishai Mandelbaum and Martin I. Reiman}, journal={Manuf. Serv. Oper. Manag.}, year={2002}, volume={4}, pages={208-227} }

The most common model to support workforce management of telephone call centers is theM/ M/ N/ B model, in particular its special casesM/ M/ N (Erlang C, which models out busy signals) andM/ M/ N/ N (Erlang B, disallowing waiting). All of these models lack a central prevalent feature, namely, that impatient customers might decide to leave (abandon) before their service begins.In this paper, we analyze the simplest abandonment model, in which customers' patience is exponentially distributed and…

## 585 Citations

Application of queueing models with abandonment for Call Center congestion analysis

- Computer Science
- 2020

It is shown that the M/M/c+G analytical queueing models with abandonment, with patience time represented by generic distributions (particularly mixed distributions), are more effective than the M-M-c+M analytical queues with abandonment with Exponential patience, commonly used to evaluate congestion problems in Call Centers and support sizing and operational decisions in these systems.

Designing a call center with an IVR (Interactive Voice Response)

- Computer ScienceQueueing Syst. Theory Appl.
- 2010

A Markovian model for a call center with an IVR is studied, which approximate operational performance measures, such as the probability for a busy signal and the average wait time for an agent, in an asymptotic regime known as QED or the Halfin–Whitt regime, which accommodates moderate to large call centers.

Engineering Solution of a Basic Call-Center Model

- Computer Science, EngineeringManag. Sci.
- 2005

An algorithm is developed to rapidly compute approximations for all the standard steady-state performance measures in the basic call-center queueing modelM/GI/s/r+GI, which has a Poisson arrival…

Call Centers with Impatient Customers: Many-Server Asymptotics of the M/M/n + G Queue

- Computer ScienceQueueing Syst. Theory Appl.
- 2005

Empirical findings have demonstrated a robust linear relation between the fraction abandoning and average wait, and the QED and QD formulae provide excellent approximation for exact M/M/n + G performance measures.

Call center operation model as a MAP/PH/N/R−N system with impatient customers

- Mathematics, Computer ScienceProbl. Inf. Transm.
- 2011

An algorithm for finding the stationary distribution of system states and derive formulas for basic performance characteristics are given and Laplace-Stieltjes transforms for sojourn and waiting times are found.

Staffing Many-Server Queues with Impatient Customers: Constraint Satisfaction in Call Centers

- Computer ScienceOper. Res.
- 2009

This work considers a constraint satisfaction problem, where one chooses the minimal staffing level n that adheres to a given cost constraint, and proposes a new ED + QED operational regime that enables QED tuning of the ED regime.

Adaptive Behavior of Impatient Customers in Tele-Queues: Theory and Empirical Support

- Economics, Computer ScienceManag. Sci.
- 2002

This paper addresses the modeling and analysis of abandonments from a queue that is invisible to its occupants, and proposes an M/M/m-based model that incorporates adaptive customer behavior and establishes the existence and uniqueness of the operating point in steady state.

On first-come, first-served queues with two classes of impatient customers

- Mathematics, Computer ScienceQueueing Syst. Theory Appl.
- 2019

A virtual waiting time process is introduced where the service times of customers who will eventually abandon the system are not considered and the performance measures of the M/M/k + M system serve as good approximations of the system based on real data.

Many-server queues with customer abandonment: A survey of diffusion and fluid approximations

- Computer Science
- 2012

This survey paper focuses on G / GI / n + GI parallel-server queues that serve as a building block to model call center operations and results include the performance insensitivity to patience time distributions and diffusion and fluid approximate models as practical tools for performance analysis.

The impact of retrials on call center performance

- Computer ScienceOR Spectr.
- 2004

This paper models a call center as a Markovian queue with multiple servers, where customer balking, impatience, and retrials are modeled explicitly, and explores the retrial phenomenon for a real call center.

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