Cross-Layer Design of Opportunistic Spectrum Accessin the Presence of Sensing Error

摘要

We address the design of cognitive MAC protocols forrnopportunistic spectrum access in the presence of sensing error. Decentralizedrnprotocols are presented for ad hoc networks where therernis no central coordinator or dedicated communication/control channel.rnSecondary users search for and access spectrum opportunities independentlyrnwithout exchanging local information on spectrum availability.rnWe assume on-demand partial spectrum monitoring subject to sensingrnerrors. Specifically,a secondary user may not be able to simultaneouslyrnsense the whole spectrum of interest due to hardware limitation andrnmay only monitor the spectrum when it has data to transmit in order tornconserve energy.We propose two approaches to formulating opportunisticrnspectrum access in the presence of sensing error by considering either arnconstraint on the probability of colliding with primary users or a penaltyrnimposed on each collision. Under these formulations,we address the jointrndesign of both the spectrum sensor at the physical layer and the cognitivernprotocol at the MAC layer to maximize spectrum efficiency while limitingrnthe interference to primary users.