Energy-efficient channel aggregation in cognitive radio networks with imperfect sensing

In this paper, we study energy-efficient channel aggregation problem in cognitive radio networks, where a secondary user senses multiple channels simultaneously or sequentially in the sensing period and subsequently aggregate those channels sensed free. We aim at designing the optimal sensing time and power allocation to achieve the maximum energy efficiency, meanwhile considering the maximum transmit power and minimum rate constraints as well as the protection to primary users. Taking into account the dynamics of the primary users' activities and the impact of imperfect spectrum sensing, we formulate the above design problem as a sum-of-ratios problem and solve it by applying the theory of nonlinear fractional programs. Numerical results validate the optimality of our energy-efficient design. Moreover, the impacts of the spectrum sensing approaches, the maximum number of sensed channels and the maximum power and minimum rate constraints on energy efficiency are also investigated respectively.