====== Probabilistic data generation based age-critical frameless ALOHA protocol in wireless networks ======

===== Abstract =====
Multiple access control (MAC) protocols allow wireless devices to access a common
radio channel. Slotted ALOHA is a well-known MAC protocol employed in wireless
networks due to its several advantages. Frameless ALOHA (FA) is a variant of the
slotted ALOHA in which multiple devices send their data to a base station with equal
probability on a channel, and the base station decodes data with successive interference
cancellation. Age of information (AoI) is a critical performance metric representing the
time elapsed since the latest data that reached its destination was generated at its
sender. Age-Critical FA (ACFA), derived from FA, prohibits the transmission of those
devices that successfully recover data in the last frame, such that the average AoI
(AAoI) is reduced. Except for those prohibited devices, other devices access a frame by
sampling/generating data and then opportunistically sending data in each slot in the
frame. However, it is unnecessary for all the other devices to access frames because
letting a mere part of them attend frame access can scatter traffic more flexibly at
different times and reduce energy consumption due to less data generation. Thus, this
paper studies a modified age-critical frameless ALOHA, called Probabilistic Data
Generation based ACFA (PDG-ACFA), in which a frame access probability is
employed to determine whether a device samples and generates data. An analysis
validated through simulations is conducted to evaluate the performance of PDG-ACFA.
Numerical results show that the PDG-ACFA yields a lower AAoI under the constraint
on mean energy consumption, compared to the ACFA.