Abstract
Cognitive radio networks (CRNs) have become a promising solution to improve the spectrum utilization. However, it also brings up new challenges in wireless networks. In this thesis, we consider the multicast routing and channel allocation problems in cognitive radio networks. The goal is to construct a multicast tree and to assign the transmitting channel of each relay node such that the total transmission cost is minimized. We prove that the minimum multicast tree problem in CRNs is NP-Complete. We propose a centralized approximation algorithm to approach the minimum cost multicast tree in polynomial time. The algorithms are aimed at exploiting the broadcast nature of wireless transmissions and further reducing the total transmission cost of the multicast tree. Based on the centralized algorithm, we develop a decentralized one. The simulation results shows that the total transmission cost produced by our algorithms is less than the cost produced by other multicast routing schemes, which in turn reserves more radio resources for further usage.