Abstract
The personnel cost has been increasing in recent years. Especially, for a call center, the personnel cost has accounted for 70% of total operation cost. Therefore, recently, call center agent shift scheduling has become an important problem. This study proposes two mixed integer programming formulation to solve the long-term agent shift scheduling problem for a 24-hours call center. This formulation will find the optimal agent shift schedule. We consider more thoroughly on the government regulation in our formulation than previous literatures. Most of previous studies in this subject deal with the demand forecast and shift man power allocation problem by determining the number of people is needed for a particular shift. Only a few studies considers personnel shift schedule problem and most of them use heuristic method to solve the problem; furthermore, they use two separated steps to solve the problem. The first one is to find the man power requirement for each time period. The second one calculates the detailed shift assignment for each individual agent. The potential shortcoming of using two separated steps to solve the problem is the gap between the obtained solution and the optimal solution might be too large. The study proposes a mixed integer program formulation that can be solved in one step; thus, avoid the shortcoming of the two-step approaches. Since the number of integer variable is the major determinant for the computation time of a mixed integer program, this study proposes a number of new modeling techniques that help reducing the number of integer variables, and use the modeling techniques in second mixed integer program in this study. Although the number of integer variables of the second mixed integer program is less than that of first mixed integer program, the first mixed integer program has better solutions than the second mixed integer program when the solution time is fixed. Keywords: call center, agent shift scheduling, multiple skill agent