Abstract
It may be very difficult to achieve the optimal shift schedule in call centers which have highly uncertain and peaked demand during short time periods. Overlapping shift systems are usually designed for such cases. This paper studies shift scheduling and rostering problems for inbound call centers where overlapping shift systems are used. An integer programming model that determines which shifts to be opened and how many operators to be assigned to these shifts is proposed for the shift scheduling problem. For the rostering problem both integer programming and constraint programming models are developed to determine assignments of operators to all shifts, weekly days-off, and meal and relief break times of the operators. The proposed models are tested on real data supplied by an outsource call center and optimal results are found in an acceptable computation time. An improvement of 15% in the objective function compared to the current situation is observed with the proposed model for the shift scheduling problem. The computational performances of the proposed integer and constraint programming models for the rostering problem are compared using real data observed at a call center and simulated test instances. In addition, benchmark instances are used to compare our Constraint Programming (CP) approach with the existing models. The results of the comprehensive computational study indicate that the constraint programming model runs more efficiently than the integer programming model for the rostering problem. The originality of this research can be attributed to two contributions: (a) a model for shift scheduling problem and two models for rostering problem are presented in detail and compared using real data and (b) the rostering problem is considered as a task-resource allocation and considerably shorter computation times are obtained by modeling this new problem via CP.
Highlights
Service industry is known for its labor-intensive structure
Models studied in [8] are an Ejection Chain metaheuristic, a Branch and Price method, and an Integer Programming formulation coded on Gurobi 5.6.3
This paper addresses an integrated solution for the shift scheduling and the rostering problems within call centers
Summary
Service industry is known for its labor-intensive structure. any improvement on labor costs will result in considerable savings in total cost. Several studies on the workforce planning of the call centers focus on generating workforce schedules meeting both the necessary service levels constraints and the requirements of some laws and regulations. While generating these schedules, it is extremely hard to find good solutions. We want to focus on the issue of determining the break times As it is known, an operator usually works between seven and nine hours a day and (s)he needs breaks during this period. Staffing requirements means the minimum number of operators ensuring the service quality level within each period of the planning horizon.
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