Worst case signalling traffic for a multi-service access protocol

Modern multi-service medium access protocols use a collision based capacity request signalling channel. Such signalling channels may be based on the slotted Aloha multiaccess principle. This paper studies the performance of slotted Aloha subject to extreme inter-station correlation by means of a discrete-time Markov chain analysis. We study conditions whereby the time to collision resolution becomes unacceptably high (defined as deadlock). Three signalling channel management schemes for alleviating the deadlock problem are evaluated. Of these, the cyclic contention mini-slot (CMS) sharing technique employing multiple CMSs per data slot is the one that extends the protocol´s useable load region the furthest. We find that implementation of a scheme, which dynamically adjusts the p-persistence parameter towards its optimal value, is desirable. Both error free and error prone conditions are studied. The results highlight the fact that the critical signalling load is largely unaffected by the presence of errors, so that even in extremely error prone environments, the limiting performance factor is still the collision rate