Modeling and optimization problems in contact centers (original) (raw)

Staffing Multiskill Call Centers via Linear Programming and Simulation

Management Science, 2008

We study an iterative cutting-plane algorithm on an integer program, for minimizing the staffing costs of a multiskill call center subject to service-level requirements which are estimated by simulation. We solve a sample average version of the problem, where the service-levels are expressed as functions of the staffing for a fixed sequence of random numbers driving the simulation.

Modeling and Simulation of Call Centers

Proceedings of the Winter Simulation Conference, 2005., 2005

In this review, we introduce key notions and describe the decision problems commonly encountered in call center management. Main themes are the central role of uncertainty throughout the decision hierarchy and the many operational complexities and relationships between decisions. We make connections to analytical models in the literature, emphasizing insights gained and model limitations. The high operational complexity and the prevalent uncertainty suggest that simulation modeling and simulation-based decision-making could have a central role in the management of call centers. We formulate some common decision problems and point to recently developed simulation-based solution techniques. We review recent work that supports modeling the primitive inputs to a call center and highlight call center modeling difficulties.

Modelling and simulation of a telephone call center

Proceedings of the 2003 International Conference on Machine Learning and Cybernetics (IEEE Cat. No.03EX693), 2003

We consider a system with two types of traffic and two types of agents. Outbound calls are served only by blend agents, whereas inbound calls can be served by either inboundonly or blend agents. Our objective is to allocate a number of agents such that some service requirement is satisfied. We have taken two approaches in analyzing this staffing problem: We developed a simulation model of the call center, which allows us to do a what-if analysis, as well as continuous-time Markov chain (CTMC) queueing models, which provide approximations of system performance measures. We describe the simulation model in this paper.

Simulation-based optimization of agent scheduling in multiskill call centers

2008

We examine and compare simulation-based algorithms for solving the agent scheduling problem in a multiskill call center. This problem consists in minimizing the total costs of agents under constraints on the expected service level per call type, per period, and aggregated. We propose a solution approach that combines simulation with integer or linear programming, with cut generation. In our numerical experiments with realistic problem instances, this approach performs better than all other methods proposed previously for this problem. We also show that the two-step approach, which is the standard method for solving this problem, sometimes yield solutions that are highly suboptimal and inferior to those obtained by our proposed method.

A Simple Staffing Method for Multiskill Call Centers

Manufacturing & Service Operations Management, 2008

W e study a simple method for staffing in multiskill call centers. The method has short computation times and determines nearly optimal staffing levels. It is in both views competitive to other methods from the literature. Because of the fast and accurate performance of the method, many different scenarios can be analyzed, and our method can be used for both tactical and strategic capacity management decisions.

Optimizing the Staffing and Routing of Small-Size Hierarchical Call Centers

Production and Operations Management, 2008

M ultiple-skill call centers propagate rapidly with the development of telecommunications. An abundance of literature has already been published on call centers. Here, we want to focus on centers that would typically occur in business-to-business environments; these are call centers that handle many types of calls but where the arrival rate for each type is low. To find an optimal configuration, the integrality of the decision variables is a much more important issue than for larger call centers. The present paper proposes an approach that uses elements of combinatorial optimization to find optimal configurations. We develop an approximation method for the evaluation of the service performance. Next, we search for the minimum-cost configuration subject to service-level constraints using a branch-and-bound algorithm. What is at stake is to find the right balance between gains resulting from the economies of scale of pooling and the higher cost or cross-trained agents. The article shows that in most cases this method significantly decreases the staffing cost compared with configurations with only cross-trained or dedicated operators.

Telephone Call Centers: Tutorial, Review, and Research Prospects

2003

Telephone call centers are an integral part of many businesses, and their economic role is significant and growing. They are also fascinating socio-technical systems in which the behavior of customers and employees is closely intertwined with physical performance measures. In these environments traditional operational models are of great value -and at the same time fundamentally limited -in their ability to characterize system performance.

Managing trade-offs in call center agent scheduling: methodology and case study

Summer Computer Simulation Conference, 2007

This paper develops a flexible and tractable scheduling methodology that produces near-optimal call center agent schedules while taking into account the costs associated with customer waiting time, customer abandonment, and call center agents. Our methodology combines integer programming (to find a desirable staffing plan for a given total number of agents) and simulation modeling (to evaluate the weekly costs of a given staffing plan). We describe the advantages of this approach over the traditional scheduling method, and test both methods by building schedules based on actual demand and shift data from an actual call center operated by Expedia.com under a variety of cost scenarios. The new scheduling approach not only out-performs the traditional staffing approach in all scenarios examined, it reduces total weekly costs of the call center's existing agent schedule by 8-25%, depending on the scenario.

Call center performance evaluation

2005

In this paper, the effect of using a combination of multiskill and specialized agents on the performance of a call center is studied. An OPNET simulator for the call center has been designed, implemented, and verified. The designed simulator has the flexibility that facilitates comparison of different scenarios. The scenarios are mainly oriented toward finding the performance enhancement that could be gained by using a combination of multi-skill and specialized agents. As the usual case in such problems, there must be an optimum combination that results in the best performance for a lower cost. The designed simulator provides a very powerful and scalable tool that could be used to find such an optimum, and could be easily modified to support larger call centers. Some selected scenarios have been tested and the results introduced and analyzed. The result of our research concludes that the economies of scale could be obtained by cross training only a minor fraction of agents.