Spectrum Sensing in small-scale networks: Dealing with multiple mobile PUs

The emerging applications of the small-scale primary-user (PU) paradigm require Cognitive Radio (CR) networks to explicitly support the mobility of a multitude of PUs, concurrently using the same spectrum band. In this paper, the effects of multiple mobile PUs on the spectrum sensing functionality are analyzed to jointly maximize the sensing efficiency and the sensing accuracy. To this aim, as first, a new mathematical model (the aggregate PU model) is proposed to effectively describe the cumulative effects of multiple mobile PUs on the spectrum sensing functionality. Then, stemming from this model, closed-form expressions for the sensing time and the transmission time that jointly maximize the sensing efficiency and the sensing accuracy are derived. Through the derived closed-form expressions, the following fundamental questions are answered: (i) How long can a CR user transmit without interfering with the multiple mobile PUs? (ii) How long must a CR user observe a targeted spectrum band to reliably detect multiple mobile PUs? All the theoretical results are derived by adopting a general mobility model for the multiple mobile PUs. The analytical results are finally validated through simulations.