On monotone optimal policies in a queueing model of M/G/1 type with controllable service time distribution

A queueing model of M/G/1 type with controllable service time distribution is considered in this paper. Conditions on costs and service time distribution only are established such that there exists a monotone policy optimal relative to the average cost criterion. To prove this, it is shown that it suffices to search for a monotone optimal policy in a Markov decision model associated with the queueing model.