Energy-efficient power allocation algorithms for OFDM-based cognitive relay networks with imperfect spectrum sensing

This paper investigates the energy-efficient power allocation for orthogonal frequency division multiplexing (OFDM) based relay-aided cognitive radio networks (CRNs) with imperfect spectrum sensing considered in the system model. The object is to maximize the energy efficiency measured by the “Throughput per Joule” metric subject to the total transmit power and interference constraints. To solve the problem efficiently, the primal problem is transformed into a convex optimization problem using the fractional programming method. Optimal and suboptimal algorithms are proposed, and simulation results reveal that the proposed algorithms can obtain a good tradeoff between energy and capacity. Meanwhile, the suboptimal algorithm can reduce the computational complexity hugely with a marginal performance loss compared with the optimal algorithm.