Secondary User Harvests Energy Research Articles

Age of Information Minimization for Radio Frequency Energy-Harvesting Cognitive Radio Networks.

The Age of Information (AoI) measures the freshness of information and is a critic performance metric for time-sensitive applications. In this paper, we consider a radio frequency energy-harvesting cognitive radio network, where the secondary user harvests energy from the primary users’ transmissions and opportunistically accesses the primary users’ licensed spectrum to deliver the status-update data pack. We aim to minimize the AoI subject to the energy causality and spectrum constraints by optimizing the sensing and update decisions. We formulate the AoI minimization problem as a partially observable Markov decision process and solve it via dynamic programming. Simulation results verify that our proposed policy is significantly superior to the myopic policy under different parameter settings.

Power Allocation Scheme and Performance Analysis for Multiuser Underlay Full-Duplex Cognitive Radio Networks With Energy Harvesting

This paper introduces a comprehensive wireless energy harvesting model applied for multiple secondary users (SUs) in full-duplex cognitive radio networks. In this proposed model, SUs harvest energy from a hybrid base station (HBS), in addition to the primary user (PU) network on the downlink and transmit their data on the uplink. The opportunistic user selection scheme is employed in the SU network to achieve a better SU performance. Considering the underlay spectrum sharing paradigm, the total SU transmitted powers are limited to the maximum allowable PU interference threshold. Moreover, the proposed SU system suffers from self-interference from the transmitting antenna of the HBS and co-channel interference from the PU transmitter. Closed-form expressions for the SU system outage probability, average symbol error probability, and ergodic capacity are derived. Obtained exact expressions are then simplified to their asymptotic results in the high signal-to-noise-ratio regime. Based on these results, a power allocation optimization problem is formulated to reduce the SU outage probability under the constraints of performance indices. Computer-aided numerical and simulation work is performed to validate the exact expressions.

Secure Energy Efficiency for NOMA Based Cognitive Radio Networks With Nonlinear Energy Harvesting

In order to improve the spectrum efficiency and secrecy energy efficiency, in this paper, we propose a non-orthogonal multiple access (NOMA)-based secure scheme for cognitive radio networks. In the proposed scheme, the secondary users harvest energy from the radio-frequency signals to securely transmit the secondary privacy information with the NOMA technique. Unlike the conventional ideal linear energy harvesting, we employ the practical nonlinear energy harvesting model for energy harvesting. To implement the proposed scheme, the energy transmitter first broadcasts radio-frequency signals to power the secondary users. Then, the secondary users employ the NOMA technique to transmit the uplink privacy information, which is threatened by the eavesdropper. Considering two scenarios: two secondary users and more than two secondary users, we first provide comprehensive analysis of the secondary secrecy performances and derive the closed-form expressions of the secrecy outage probability for both scenarios. Following the above analysis, we develop the optimization problems to optimally allocate the time slot and the secondary transmit power such that the minimum secrecy energy efficiency is maximized under the constraints of the transmission security and reliability requirements. A two-stage algorithm is proposed to efficiently solve the above optimization problems. Numerical results are presented to verify the analysis in terms of the secrecy rate and secrecy energy efficiency.