Currently the research on input-queued ATM switches is one of the most active research fields.The limiting throughput of it with input queue under the FCFS scheme is 0.59.Three policies are proposed to improve the throughout of switch:input expansion policy

window selection policy and cell discarding policy.In this paper

we study performance of these scheduling algorithms

and using simulation and numerical results

we get analytic formulas that are better than available formulas in practice.