The stability region of random multiple access under stochastic energy harvesting

In this paper, we consider the random access of nodes having energy harvesting capability and a battery to store the harvested energy. Each node attempts to transmit the head-of-line packet in the queue if its battery is nonempty. The packet and energy arrivals into the queue and the battery are all modeled as a discrete-time stochastic process. The main contribution of this paper is the exact characterization of the stability region of the packet queues given energy harvesting rates for the two-node slotted ALOHA system. By stability, we refer the ability of a system to keep the queues in a bounded region, or more precisely, the existence of the limiting distribution for the joint queue length process. The analysis is non-trivial even for the two-node case because it involves the interaction between nodes of having both the packet queue and the battery. The result is obtained for both scenarios in which the capacity of batteries is infinite and also finite.