ABSTRACT
It has been generally recognized that utilization of radio spectrum by licensed wireless systems, for example, TV broadcasting, aeronautical telemetry, is quite insufficient [2]. In particular, at any given time and spatial region, there are frequency bands without signal occupancy. That is, licensed signal transmissions are sparse in time domain for a given frequency band. There has been recent interest in improving spectrum utilization by permitting secondary usage using cognitive radios [1,2]. Cognitive radios use spectrum sensing to detect if frequency bands are vacant or not, and determine cognitive signal transmissions on such frequency bands to satisfy regulatory constraints of avoiding interference to authorized users.
