Adaptive sensing for increased spectrum utilization in dynamic cognitive radio systems

Cognitive radios (CR) are regarded as a viable solution to enabling flexible use of the frequency spectrum in future generations of wireless systems by taking advantage of spectrum holes, that is idle frequency bands not actively used by primary users (PU) for licensed transmissions. The actual utilization of a spectrum hole is determined by its duration (implied by the time interval between two PU transmissions) as well as by the time needed to detect it through a spectrum sensing procedure. In this paper we propose a new method for adapting the duration of the spectrum sensing window that improves the probability of detection of the spectrum holes as well as their actual utilization. The proposed method is illustrated with numerical results obtained from simulations which show that both the spectrum sensing performance (evaluated in terms of the probabilities of detection and false alarm) and the hole utilization are improved when compared to a scheme with fixed sensing window length.