Optimal admission control in cognitive radio networks

We study a cognitive radio system in which the spectrum handover technique is applied by secondary users when they have to vacate a channel due to a primary user arrival. In order to limit the forced termination probability of secondary users a fractional guard channel reservation scheme is applied to give priority to spectrum handovers over new arrivals. We show that, contrary to what has been suggested, the reservation parameter cannot be adequately adjusted as a result of maximizing the throughput of secondary users. Instead we propose and explore two alternative configuration methods. The proposed methods are based on optimization problems that target the existing trade-off between blocking new sessions of secondary users and dropping ongoing ones. Additionally in our numerical experiments we identify some interesting and counterintuitive phenomena.