Energy-Harvesting Cognitive Radio Systems Cooperating for Spectrum Sensing and Utilization

In this paper, we study an energy-harvesting cognitive radio (CR) system where each secondary user (SU) harvests energy to recharge its battery. Cooperative spectrum sensing is employed to enhance the sensing performance. In this energy- constrained scenario, the SUs, as per their energy-arrival rates, can cooperate to achieve higher opportunistic spectrum utilization and improved primary user (PU) detection. For a heterogeneous CR system with different sensing environment and energy-arrival process at each SU, the optimal probability of sensing is obtained for each SU to maximize the SU network throughput while satisfying the PU collision and energy-causality constraints. SOSTOOLS is employed to solve the polynomial optimization problem, and a suboptimal scheme which can be used for larger systems is proposed. Furthermore, under a homogeneous scenario, it is shown that with a minimum number of SUs cooperating, the CR throughput performance can overcome the energy- causality and PU collision constraints.