On the output of tandem queues

The aim of this paper is to study the effect of neglecting the interdependencies in the input process at machines in a production line. Towards this end, we consider a two node tandem queue with non-exponential service times at the first node with unlimited buffer size. We investigated the output process – which forms the input for the second node. More specifically, we calculated the correlation coefficient r between two successive interdeparture intervals for several service time distributions with known as well as unknown Laplace transforms. In almost all the cases, the numerical value of r turned out to be very small. Hence approximating the behaviour at the second node by a (G/M/1) queue, we extended our study to the output process at the second node.