Resource Allocation in Multi-Cluster Radio Networks With Energy Harvesting Hybrid Multi-Channel Access

ABSTRACT Cognitive radio and energy harvesting techniques have been able to provide insight for solutionsto the inefficiency in spectrum utilization and the effects of the limited storage capacity of energy batteries.Nevertheless, the requirement for interference constraint for primary user (PU) protection, the quality ofservice (QoS) requirements of the SUs, and the low power density of the ambient electromagnetic waveshave restricted the performance of the radio frequency powered cognitive radio networks (RF-CRNs) interms of the achievable data rate for specific energy budget or sufficient energy budget for target data rate.We are therefore motivated to investigate a radio frequency powered cognitive radio (RF-CR) with thecapacity for improved achievable throughput and energy harvesting. Our model consists of multiple PUsand SUs coexisting in a practical overlapping clustered network. In each time frame for the adopted timedivision multiple access (TDMA) technique, SUs can exploit the multi-user benefit to harvest energy fromboth the PU and SUs transmissions for improved active probability. Therefore, taken into considerationthe heterogeneity of each SUs in terms of their signal-to-noise (SNR), the energy harvesting rates andthe inter- and intra-cluster interference, the problem is formulated into a fractional nonlinear optimizationto determine the sensing duration, and power allocations that maximize the average energy efficiencyof the RF-CRN subject, to constraints on energy causality, and PU protection. The performance of theproposed hybrid multi-channel access scheme is studied in terms of the trade-off between the total achievablethroughput by the secondary users and the interference generated among others. Simulation results showthat a trade-off exists between achieving optimal spectral efficiency and energy efficiency and, the optimaltransmit power therefore depends on the primary design objective. Results equally show that the proposedhybrid multi-channel access scheme outperforms the existing scheme in literature.