Many `output-scheduling' algorithms have been proposed for improving the performance of input queueing asynchronous transfer mode (ATM) switches, whereby cells from different random-access input queues destined for the same output can be scheduled for non-conflicting transmissions. An optimal output-scheduling algorithm, one with the full coordination of transmissions to all outputs, can approach the performance of output queueing. Because of the complexity of such an optimal scheduler, output schedulers proposed in the literature are without such coordination. We propose a simple way to incorporate such a full coordination in output-scheduling with much simple hardware, for small size switches. Throughput of the input queueing switch thus approaches that of the output queueing switch, without speed-up, input/output grouping or complicated hardware. To make the output-scheduling algorithm fast enough, we incorporate parallelism and pipelining. We perform detailed simulation study of the performance of the input queueing switch with the proposed scheduling algorithm.

In this paper, we propose a dynamic TDMA with priority-based request packet transmission scheme (D-TDMA/PRPTS) which applies priority-based request packet transmission scheme instead of slotted ALOHA (S-ALOHA). D-TDMA/PRPTS can avoid collisions between voice request packets and data request packets and transmit voice request packets preferentially. This makes D-TDMA/PRPTS enlarge the system capacity for voice users with SAD. We analyze voice packet dropping probability and channel utilization for voice traffic by using an appropriate Markov model. We also present simulation results to verify the analysis and to investigate data performances as well, with the voice-data integrated scenario.