Performance and stability analysis of buffered slotted ALOHA protocols using tagged user approach

This paper presents a new approximation approach to analyze slotted ALOHA (S-ALOHA) systems with finite user population having either finite or infinite user buffer capacity. By assuming a symmetric channel, the performance analysis of the overall system is determined by the performance of an arbitrarily selected user, called the tagged user. The service time distribution for the tagged user buffer is found using a state flow graph. This distribution is then applied to the queueing analysis of the tagged user using available classical queueing theory results. The proposed approach can be applied to analysis of systems with a very large user population and user buffer capacity. The distributions and mean values of the important performance indices such as waiting time, queue size, and interdeparture time are obtained. The stability of the system with infinite buffer capacity is also studied. The region of transmission probability p in which the system is always stable and has best performance is obtained. Though the system with finite buffer capacity is considered to be always stable, a comprehensive analysis of the equilibrium points in the system is presented. The analysis presented will allow a proper choice of transmission probability so that the system always operates at the desired equilibrium point.