Enhanced spectrum utilisation in dynamic cognitive radios with adaptive sensing

Cognitive Radio (CR) is a new concept in wireless communication systems that aims at enabling dynamic access to the frequency spectrum for unlicensed secondary users (SU) through the reuse of licensed frequencies. Specifically, CR systems are expected to detect idle licensed frequencies (spectrum holes) by applying a spectrum sensing procedure, to take advantage of them for providing service to the SU, and to release them to the licensed primary users (PU) upon request. The duration of the spectrum sensing procedure is an overhead factor that affects the actual utilisation of the spectrum by the CR system and whose adaptation may enhance spectrum utilisation: the less time the CR spends for spectrum sensing and identifying spectrum holes, the more time the spectrum is available for secondary use by the CR. In this paper, we define a formal measure for spectrum hole utilisation in dynamic scenarios and propose a new method for adapting the duration of energy-based spectrum sensing that improves the detection of PU signals as well as the utilisation of spectrum holes by the SU. The proposed method is illustrated with numerical results obtained from simulations which confirm its effectiveness.