We consider spectrum
sensing strategies used to discover available spectrum in Cognitive Radio
Networks (CRNs), using both non-cooperative sensing and cooperative sensing approaches.
After introducing the background to sensing techniques, this position paper
focuses on strategies and algorithms for conducting sensing such that the sensing
time and energy are minimized, and the likelihood of finding available spectrum
is maximized. The paper mainly focuses on two approaches. The first is the
ordering of channels to be sensed, and the second is cooperative spectrum
sensing. After discussing the available strategies under each of these two
approaches, we introduce our own proposed approaches. We first introduce a
method for sorting the channels to be sensed in order to optimize the sensing time,
while satisfying PUs’ protection and false alarm constraints. Then, we
introduce a framework for cooperative sensing of multiple PUs’ channels by a
group of SUs. The framework includes strategies for assigning different SUs to
sense different PUs’ channels, selection of the fusion center for each of the
SUs clusters, and routing sensing data within the cluster from the SUs to the
fusion center. We show how this framework is capable of optimizing different
objective functions. Several open problems and future research directions are
also introduced.