Online Transmission Control for Random Access With Multipacket Reception and Reservation

A larger capacity of random access (RA) channel is demanded to cope with massive accesses from Internet of Things (IoT) devices. To do this, this work proposes multipacket reception (MPR) S-ALOHA with reservation: When making a successful RA, the user can reserve the channel for the next slot transmission with probability
$r$
, if its queue is not yet empty. This reservation can be continued with probability
$r$
until its queue becomes empty. In this system, as the number of the reserved channels grows, the number of available capacity for RA reduces. Thus, the number of RA attempting users needs to be controlled to avoid collision, whereas the unbounded growth of other users’ queue should be prevented. This work analyzes the throughput and stability condition of the proposed system and designs a throughput-optimal backoff algorithm based on the backlog size estimation. In the numerical studies, MPR S-ALOHA without reservation and time division multiple access (TDMA) are compared as benchmarks. As a result, it is proven that as
$r\rightarrow 1$
, the MPR channel capacity is fully utilized if the proposed RA algorithm is jointly used with the reservation scheme. Moreover, it is demonstrated that the system can be also stabilized by the proposed backoff algorithm.