A Novel Analytical Modeling of Composite Cognitive Capability with an Overlay Sensing Approach

Cognitive radios are promising solutions to the problem of overcrowded spectrum. The cognitive capability is the key technology that enables the secondary users to use licensed spectrum in a dynamic manner that the spectrum of the primary users are as unaffected as possible. But the metrics for composite cognitive capability are required in time in order to capture the temporal, spectral, and spatial variations (“spectrum holes”) simultaneously with cognitive signal strength under sophisticated cognitive radio environments. In this paper, in order to evaluate the spectrum awareness effectively, a novel analytical modeling of composite cognitive capability with an overlay sensing approach is proposed. A cognitive scenario with elliptically spatial variations is assumed, which consists of primary units and cognitive radio units (CRUs) with concurrent temporal and spectral scanning schemes. Moreover, a metric of spectrum holes ratio (SHR) is defined to evaluate the composite cognitive capability. Furthermore, CRUs can also detect transmission signals strength and “assist” receiving signal through a tone-assisted relaying signal to enhance system performance and reach lower symbol error probability with a specific tone-to-signal ratio above signal-to-noise ratio decision thresholds under a constant elliptic SHR locus.