Overflow analysis and Cross-trained Servers

In this paper, we aim to evaluate the performance of a call center composed of specialized and cross-trained operators (i.e. operators trained to answer different classes of calls). The paper focuses on the approximation of the loss probability of a call center where the different classes of calls arrive according to a Poisson distribution and service time distribution is exponential. We make the simplifying assumption that calls not immediately answered are lost. Our closed form approximation is based on an approximation for hierarchical overflow systems in telecommunication developed by Hayward and later extended by Fredericks (1980)