Power Allocation Algorithms for OFDM-Based Cognitive Radio Systems

In this paper, we investigate an optimal power allocation algorithm for OFDM-based cognitive radio. In the model of power allocation, we set the interference constraints for each primary user, and also take subcarrier sidelobes interference (adjacent channel interference (ACI)) into account, when we use the optimal power allocation algorithm, the transmission capacity of secondary users (SU) is maximized while the interference introduced to the primary user (PU) is within a certain range. Because of high complexity of the optimal power allocation algorithm, we also propose two suboptimal power loading algorithms. Simulation results show that the performance of the optimal power allocation algorithm and two suboptimal power loading algorithms is better than conventional water-filling algorithm and uniform power loading algorithm.