Demand-assigned multiple-access schemes using collision-type request channels: priority messages

Demand-assigned multiple-access (DAMA) schemes in which requests for communication channels are transmitted over shared collision-type channels to a master controller, and in which messages of different priorities are present, are analysed. Priority use of the request channels is achieved by having users select among those channels according to a priority-dependent probability distribution. Two important schemes of this class are considered. Additionally, three schemes for priority assignment of message channels are treated: two are non-pre-emptive and one is pre-emptive. Trade-offs among bandwidth utilisation and delay are considered, as well as optimisation of system parameters.