Stationary distribution of queue length in G / M / 1 queue with two-stage service policy

We consider a G / M / 1 queue with two-stage service policy. The server starts to serve with rate of μ<Subscript>1</Subscript> customers per unit time until the number of customers in the system reaches λ. At this moment, the service rate is changed to that of μ<Subscript>2</Subscript> customers per unit time and this rate continues until the system is empty. We obtain the stationary distribution of the number of customers in the system. Copyright Springer-Verlag 2006