A Novel Composite Cognitive Capability Modeling 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＂) with cognitive signal strength under a sophisticated cognitive radio environment. In this paper, in order to evaluate the spectrum awareness effectively, a novel analytical modeling of composite cognitive radio capability with an overlay sensing approach is proposed. An elliptic cognitive scenario with spatial variations is assumed, which consists of traditional primary units (PUs) and cognitive radio units (CRUs) with concurrent temporal and spectral scanning schemes. In addition, in a cooperative overlay sensing approach, the CRU will also detect the primary transmission signals for spectrum holes and ＂assist＂ the primary 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 (TSR) above SNR decision thresholds.