Turgay Türker

Bio: Turgay Türker is an academic researcher from Sakarya University. The author has contributed to research in topics: Scheduling (computing) & Constraint programming. The author has an hindex of 1, co-authored 2 publications receiving 7 citations.

An Integrated Approach for Shift Scheduling and Rostering Problems with Break Times for Inbound Call Centers

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.

An MIP model to schedule the call center workforce and organize the breaks

Abstract: In modern economies, companies place a premium on managing their workforce efficiently especially in labor intensive service sector, since the services have become the significant portion of the economies. Tour scheduling is an important tool to minimize the overall workforce costs while satisfying the minimum service level constraints. In this study, we consider the workforce management problem of an inbound call-center while satisfying the call demand within the short time periods with the minimum cost. We propose a mixed-integer programming model to assign workers to the daily shifts, to determine the weekly off-days, and to determine the timings of lunch and other daily breaks for each worker. The proposed model has been verified on the weekly demand data observed at a specific call center location of a satellite TV operator. The model was run on both 15 and 10 minutes demand estimation periods (planning time intervals).

Staffing and scheduling flexible call centers by two-stage robust optimization

Abstract: We study the shift scheduling problem in a multi-shift, flexible call center. Differently from previous approaches, the staffing levels ensuring the desired quality of service are considered uncertain, leading to a two-stage robust integer program with right-hand-side uncertainty. We show that, in our setting, modeling the correlation of the demands in consecutive time slots is easier than in other staffing approaches. The complexity issues of a Benders type reformulation are investigated and a branch-and-cut algorithm is devised. The approach can efficiently solve real-world problems from an Italian call center and effectively support managers decisions. In fact, we show that robust shifts have very similar costs to those evaluated by the traditional (deterministic) method while ensuring a higher level of protection against uncertainty.

Workforce planning and management FIT in call centers

Abstract: These issues may increase with the significant levels of uncertainty entrenched in high workloads and peak demands at flexible working schedules set by three common scenarios: 1. Overstaffing: The workload level may be lower than expected; most employees become idle, resulting in high costs. 2. Understaffing: The workload level may be higher than expected, leading to long and irregular waiting times by the clients.

A Mathematical Model for Scheduling and Rostering of Staff with Real-Life Considerations: The Case of Indian Call Centres

Abstract: AbstractIn this paper, we consider the deterministic multi-skill employee call centre problem that considers staff scheduling and rostering. In this problem, we study the allocation of flexible shifts with the flexibility of starting the shift at the beginning of any hour of a day to both multi-skilled full-time employees and multi-skilled part-type employees who can handle the respective specific types of calls during the respective shift, thereby leading to combined problem of shift scheduling and rostering. In addition, we incorporate the days off scheduling and flexible break assignment in terms of the time of commencement of the break appropriately to every full-time employee and every part-time employee. Such real-life considerations demand the problem of shift scheduling and rostering to be solved in an integrated manner, and that too, by tracking every employee’s flexible shift assignment and rostering that depend upon the specific skill set of that employee to meet the demand of attending to specific types of calls (i.e. the construction of line of work over the planning horizon). We propose a mixed-integer linear programming (MILP) model with the objective of maximizing the total number of calls attended by the employees (i.e. maximizing the total number of tasks assigned). In our computational experiments, we generate many problem instances and present the results of the computational evaluation of the MILP model. We also present an illustration to bring out the impact of the flexible shift commencement in comparison to the fixed-shift scheduling with respect to employees.KeywordsCall centreFull-time and part-time staffSchedulingFlexible shiftDays offFlexible break assignmentSkill setRosteringMixed-integer linear programming

A Duty Scheduler for Veterinary Teaching Hospitals Using Tabu Search Algorithm

Abstract: This research deals with the design, developing and testing of web-based duty scheduling system to schedule staff on a monthly basis so that a staff can have access to their duty roster irrespective of his/her location. The Federal University of Agriculture Veterinary Teaching Hospital was used the case study for this work. A computer web based system called “Veterinary Duties Scheduler” was developed to this effect using PHP as the programming language, MySQL as the database and Unified Modelling Language (UML) as system design tool. After the new system was implemented, the results gotten showed clearly that staffs were now able to view their duty roster from any location by simply logging into the system using their staff-id and password. Therefore, the new system was able to solve most of the problems associated with the existing manual system of duty scheduling as witnessed in the case study.