Performance analysis of input queue with combination of push-out and state-dependent scheduling schemes for nonblocking ATM switches

In this paper, assuming two classes of input traffic, we analyze a combination of push-out and general state-dependent scheduling schemes applied to input queues of nonblocking ATM switches with the speed-up factor ≥ 1. The analysis is done in two steps in the discrete-time domain, using an embedded semi-Markov process (SMP) concept (Takagi, 1993). In numerical examples for some specific scheduling schemes, we compare the performances and show that reasonable performance differences both in loss probabilities and in waiting times can be achieved between two classes over a wide range of the offered load. We also show that all the priority schemes considered in this paper allow higher utilization of the switch than the non priority one, and among them the queue length threshold (QLT) scheduling scheme gets the highest utilization. Lastly, we note that although the analysis assumes an infinitely large size switch, the result gives a quite accurate approximation for finite size switches with around one hundred input/output ports.