Cognitive radio networks (CRNs) open up the
underutilized parts of the licensed spectrum for secondary reuse, so long as
this secondary access does not cause harmful interference to the licensed
users. Being able to run CRNs in a completely decentralized manner, as opposed
to centralized operation, can be quite advantageous, because it avoids the
complexity and single point-of-failure issues that arise from the presence of a
central controller, and also eliminates the difficult step of establishing and
maintaining a common control channel, which can suffer from saturation and
malicious attacks. To that end, we propose in this paper a novel decentralized
spectrum allocation technique for CRNs that not only provides great performance
in terms of high throughput, excellent fairness, and minimal interference
between cognitive users but also provides very stable network operation, in
which cognitive users do not have to switch their operating frequency quite
regularly. This is achieved by systematically observing the history of the
spectrum usage to determine the proper channel assignment in the CRN. Our
proposed technique is intuitive, is completely decentralized, and allows for
quick reaction to changes in the CRN, such as when the primary users licensed
to use the spectrum are suddenly activated.