Comments on "Optimal Utilization of a Cognitive Shared Channel with a Rechargeable Primary Source Node"

TL;DR

This paper critiques a recent study on a cognitive shared channel with a rechargeable primary node, clarifying that the primary energy queue capacity does not influence the network's stability region under the proposed model.

Contribution

It corrects the previous analysis by showing the primary energy queue capacity has no effect on the stability region in the given queueing model.

Findings

Energy queue capacity does not affect the stability region.

The previous finite energy queue results are incorrect.

The primary energy queue behaves as an M/D/1 queue with Bernoulli arrivals.

Abstract

In a recent paper [1], the authors investigated the maximum stable throughput region of a network composed of a rechargeable primary user and a secondary user plugged to a reliable power supply. The authors studied the cases of an infinite and a finite energy queue at the primary transmitter. However, the results of the finite case are incorrect. We show that under the proposed energy queue model (a decoupled ${\rm M/D/1}$ queueing system with Bernoulli arrivals and the consumption of one energy packet per time slot), the energy queue capacity does not affect the stability region of the network.