  The rapidly growing number of wireless devices running applications that
require high bandwidths, has resulted in increasing demands for the unlicensed
frequency spectrum. Given the scarcity of allocated unlicensed frequencies,
meeting such demands can become a serious concern. Cognitive Radio
(CR)technology opens the door for the opportunistic use of the licensed
spectrum to partially address the issues relevant to the limited availability
of unlicensed frequencies. Combining CR and Wi-Fi to form the socalled White-Fi
networks, has been proposed for achieving higher spectrum utilization. This
article discusses the spectrum sensing in White-Fi networks and the impacts
that it has on the QoS of typical applications. It also reports the analysis of
such impacts through various simulation studies. Our results demonstrate the
advantages of an adaptive sensing strategy that is capable of changing the
related parameters based on QoS requirements. We also propose such a sensing
strategy that can adapt to the IEEE 802.11e requirements. The goal of the
proposed strategy is the enhancement of the overall QoS of the applications
while maintaining efficient sensing of the spectrum. Simulation results of the
scenarios that implement the proposed mechanisms demonstrate noticeable QoS
improvements compared to cases where common sensing methods are utilized in
IEEE802.11 networks.
