A Hybrid Communication Scheme for Throughput Maximization in Backscatter-Aided Energy Harvesting Cognitive Radio Networks

Motivated by the benefits of cognitive radio (CR), energy harvesting (EH), and backscatter communication (BC) technologies to support Internet of Things (IoT) systems, we investigate the backscatter-aided EH CR networks (EH-CRNs) in a multichannel scenario. To achieve high throughput on various channels, we propose a novel hybrid communication scheme that the secondary transmitter (ST) selects one channel for spectrum sensing, and performs multiple actions based on the sensing result. To be specific, if the selected channel is detected as busy, the ST potentially performs underlay mode transmission, ambient BC (AmBC), or radio frequency (RF) EH. Otherwise, the ST performs interweave mode transmission. Based on the ST’s knowledge of the channel availability and the amount of the available energy, the decisions of channel and specific action selections are made. Furthermore, the sequential decision problem is formulated as a mixed observability Markov decision process (MOMDP), and addressed by the classic value iteration algorithm. The proposed scheme could be flexibly adapted to the changes in energy and channel availabilities. Simulations demonstrate the superiority of this scheme in terms of throughput, and show that even without channel selection, the proposed scheme conducted on the channels with different idle probabilities always achieves high throughput.

I. Introduction

Recently, the number of Internet of Things (IoT) devices has rapidly increased, and the competition for wireless spectrum has become increasingly fierce, resulting in a serious spectrum scarcity problem in the IoT. On the one hand, the demand for wireless spectrum resources has boomed. On the other hand, a significant amount of spectrum is underutilized [1]. To alleviate the problem of spectrum scarcity and improve the spectrum utilization, cognitive radio (CR) [2], [3] has been proposed for the development of IoT as an effective technology. In CR networks (CRNs), unlicensed users [i.e., secondary users (SUs)] adjust transmission parameters based on the observations about the environment, in order to adapt to the environment changes. To be specific, secondary transmitters (STs) are allowed to periodically perform spectrum sensing and opportunistically access the channels licensed to primary users (PUs).