Energy Efficiency Analysis of a Feedback-Aided IRSA Scheme

Irregular Repetition Slotted ALOHA (IRSA) achieves load thresholds very close to 1 at the expense of reduced energy efficiency compared to its competitor, Coded Slotted ALOHA (CSA). The efficiency is related to the expected number of transmitted replicas, and is upper-bounded by 0.5 in the case of IRSA. In this paper, we present a feedback-aided IRSA scheme, analyze its efficiency, and show that utilizing a very limited feedback will offer considerable improvements. Remarkably, the feedback-aided scheme enables IRSA to achieve efficiencies greater than 0.5, and in some cases, perform very close to the more complex CSA schemes.