Link Restoration in Cognitive Radio Networks

Cognitive radio (CR) technology can achieve higher spectrum efficiency by exploring the unused spectrum in licensed band. Most of the existing work focuses on maximizing the spectrum utilization but ignores the immediate influence from primary users to network throughput. In this paper, we investigate the importance of planned link restoration in cognitive radio networks. We formulate the link restoration problem as an integer programming problem. By considering both channel assignment and interference between links, the link through-put can be guaranteed even when primary users appear, and therefore can provide the needed reliability for real-time wireless applications. We consider a link failure model which captures the induced link failures from multiple primary users operating on one frequency channel. Under this failure model, our algorithm explores the sharing of backup capacity. We compare our algorithm to two baseline restoration schemes. Our algorithm performs very well in terms of capacity usage and throughput reliability. By reserving 24.8% of network capacity, our algorithm meets the guarantee requirement in all simulation cases, while "no restoration" just meets the guarantee requirement in 50.8% of all simulation cases.