Probability-Based Transmit Power Control for Dynamic Spectrum Access

To take advantage of time-varying spectrum opportunities, a cognitive radio (CR) user continuously monitors the dynamic usage of the licensed frequency band and is allowed to utilize the spectrum resource when it does not cause unacceptable interference with licensed users. In this paper, the transmit power control scheme for each data transmission between periodic spectrum sensing activities is proposed to improve the performance of the CR user with utilization of the statistics of the licensed band occupancy. While the conventional CR transmission scheme allocates the same transmit power to each data sample, our scheme varies the transmit power dynamically according to the non-interfering probability at each sample so that the effective transmission rate of the CR user increases and the expected interference level with the licensed communication decreases. Detection errors are also incorporated into the analysis. It is demonstrated by numerical results that our scheme considerably improves the overall bandwidth efficiency while ensuring the priority of licensed users.