CSMA/PDCR: a random access protocol without priority inversion

The main goal of an access protocol that deals with different priority messages is to provide access to the common channel, at any time, to the most urgent message in the net. When this objective is not fulfilled, the priority inversion phenomenon is produced with a degradation in the quality of service offered by the protocol. The protocol that we present, CSMA/PDCR (carrier sense multiple access/priority deterministic collisions resolution), is a variant of the classic CSMA/CD that solves conflicts in a deterministic way guaranteeing that the transmitted message is always that of maximum priority. The study of its performance through simulation confirms the good service level offered to the high-priority messages, even when the overall traffic on the channel is heavy