Optimal control of an M/Hk/1 queueing with a removable server

This paper studies a single removable server queueing system with Poisson arrivals and k-type hyper-exponential service time distribution operating under the N-policy. The server may be turned on at arrival epochs or off at departure epochs. We show that the probability that the server is busy in the steady-state is equal to Σi=1^k qiρi. Various system performance measures, such as the expected number of customers in the system, the expected waiting time in the queue, and the expected waiting time in the system are obtained. A total expected cost function per unit time is developed to determine the optimal operating N-policy at minimum cost.