Scheduling to Improve Queue Justice

Scheduling should manage queues in a satisfactory way. Many technical applications as well as common daily life queueing situations involve humans, meaning that psychological effects and justice is of major importance, where individual perceptions of justice are strongly coupled with a fair and equal treatment of users or customers. Personal impressions of justice are often more important than classical queueing performance measures. Hence, quantifying justice is particularly well suited for evaluating queueing systems and scheduling policies with regard to human attitudes. We consider the discrimination frequency as a basis for quantifying justice, where being discriminated means to be overtaken or to wait for customers with large service requirements. For a queue to be just, an equal treatment of customers is necessary, i.e. the amount of discriminations should not excessively vary for different customers as it is often the case in commonly used scheduling policies. A new policy, MFD (Most Frequently Discriminated), is introduced and shown to be useful. We provide a comparative simulation study for queueing systems operating under the traditional FCFS and SJF policies and MFD. Our results indicate that MFD significantly improves queue justice without too much worsening mean response times. It even reduces the variance of the response time.