A decentralised channel control method for grouped ALOHA systems and drift analysis

The paper considers a recursive method for each individual user to decide the re-transmission probability to improve channel utilisation for a grouped slotted ALOHA system in the delayed first transmission (DFT) mode. In this system all the users are divided into two groups according to the signal power. The paper assumes that the total channel traffic can be formulated as a Poisson stream and each user has a counter to update an estimate of the number of backlogged users in each group according to a quadruple feedback information provided about the information received during the current slot by the base station. This information is immediately available to each user in both groups. It is shown that the optimal channel utilisation which maximises the total channel throughput can be obtained if each individual user re-transmits packets with the probability identified by this paper. A heuristic analysis for the chain drift is presented to examine the system control parameter. The simulation results show that the proposed system provides improved throughput.