Cognitive radio networks

In this article, we are interested in an important paradigm of secondary systems known as cognitive radio (CR) networks where the secondary terminals are envisioned to be capable of sensing and reasoning about the operating radio environments and thereby autonomously adjusting their transceiver parameters to exploit the underutilized radio resources in a dynamic fashion. CR networks inevitably lead to complex and sophisticated interference scenarios. This has inspired our investigation on applying IC techniques to CR networks with a special focus on mitigating the internetwork interference. We have found that a CR receiver assisted by proper IC techniques can effectively combat interference from primary networks, given that the secondary signals have dissimilar characteristics to those of primary signals. In addition, various IC techniques have been found to be useful for CR transmitters to rigidly control their emission patterns and thereby mitigate the interference caused to primary systems. Moreover, we have shown that hybrid IC schemes can be obtained by combining simple IC techniques. Our investigations have suggested that the performance of CR networks can be significantly improved by using IC technologies.