A Free Access DQRAP for a Broadcast Channel1

DQRAP (Distributed Queueing Random Access Protocol) is a random multiple access protocol for a slotted broadcast channel, shared by an infinite number of stations with bursty traffic, which can achieve a performance approaching that of a hypothetical perfect scheduling protocol (i.e. M/D/1 system). The Free Access DQRAP (FADQRAP) is an easy-to-implement version of DQRAP. FADQRAP, as does DQRAP, utilizes minislots to provide ternary channel feedback and two distributed queues to resolve queueing contention and to schedule the transmission of messages. FADQRAP thus achieves almost the same performance as DQRAP. In contrast with DQRAP, FADQRAP allows a user to transmit a message and/or request in the first slot following the message arrival regardless of the state of the channel thus freeing the users from having to sense the channel continuously. The free access DQRAP is described, its performance is evaluated, and simulation results are presented. Comparisons indicate that FADQRAP achieves significant improvement in performance over the best free access tree protocol up to date.